Last June, I wanted to sell a bicycle. Where else to unload it but on Craigslist, right? A potential buyer emailed me within hours asking for details beyond what I’d posted on the site. After receiving the new information, he said he’d come over to view the bike. Did he intend to haggle? I coached myself on how to hold the price firm. But he never showed up. When I tried to expand my initial wording that evening, I found that the post was gone despite Craigslist having promised that it would remain on the site for seven days. Bewildered, I clicked on the link the company provides to ask after the fate of disappeared postings. What happened? No answer after several tries.

Several days later, I sold the bike to a used-bike store for a third of the price I’d first sought, grumbling all the while about Craigslist’s flawed free service (the company also offers paid ads). Those were my last thoughts about the company. Until recently, that is, when Nick Nascimento emailed me his own complaints. “Craigslist is now out of control,” wrote Nascimento. “What was once the friend of small business has now become a tool to put small businesses out of business.” (For full disclosure, Nascimento once worked in advertising sales for the Reader.)

Five years ago, Nascimento started AGeek2Go, LLC, a computer-servicing business operating throughout San Diego County. The company struggled at first because “in the good old days, when people had money,” Nascimento tells me, “so many just went out and bought a new computer when their old one gave them trouble.” He put the business on hold until a year and a half ago, when customers began to call asking where he’d been. At first, they turned up through word of mouth. Then, by advertising on Craigslist, Nascimento says he began to make a killing. But last summer, that changed, as Craigslist began to remove his posted ads.

Nascimento and I are meeting at the On the Border restaurant on Mira Mesa Boulevard. He is lunching on a fish taco between service calls, while I sample his guacamole hors d’oeuvres. We talk for a half hour before repairing to the Barnes and Noble next door, where the store’s Wi-Fi allows us to look on Nascimento’s laptop at the history of his Craigslist postings. What they show is a long series of successful posts, followed suddenly by continuous messages from Craigslist saying that the submissions were deleted.

As soon as the deletions started, Nascimento says, he immediately began asking, “Where have I screwed up? How can I suddenly be breaking the company’s rules when I’ve successfully posted the same ads previously for months? Then, to make matters worse, when I complained to Craigslist, saying that the site was running many ads that were breaking the rules while mine were not, they banned my account for 90 days.”

Last November, Craigslist reported that only 30 employees run the site from its headquarters in San Francisco. The company relies on its users to flag ads that break its “Terms of Use.” Such violations include posting too frequently or in the wrong category. But an ad that users deem “too commercial” also invites flagging, although how much commercialism will be tolerated is not specified.

In an October 10, 2007 interview in Freakonomics — a blog that was then on the New York Times website — Craigslist founder Craig Newmark and chief executive Jim Buckmaster responded to the issue of ads being mysteriously flagged off the site with no subsequent explanations by the company. “With over 30 million people per month visiting our site,” said Newmark, “the most effective way to deal with bad stuff is to enlist the community in self-policing. So if you find an ad that’s wrong, please flag it, and if others agree with you and flag it themselves, then it’s removed automatically. Almost always, flagged ads that were thought to be legitimate later proved to have violated community-requested guidelines.… What works for us is the culture of trust our community has built with us. We have two core values: treat others like you want to be treated, and live and let live.”

“I am continually impressed by the wisdom and fairness of Craigslist users in setting community guidelines and then enforcing them,” added Buckmaster.

That “wisdom” seemed to be a no-show when Nascimento entered Craigslist’s “Help Forum” shortly after his posting troubles began. He shows me a number of responses he received from users, whom Craigslist allows to comment in the forum. One commenter wrote, “There you go again, blaming your FREE…ad on the entire failure of your business. Perhaps a flaw in your business plan????” Another, “Who ever you are just go away please.… TRY GETTING A LIFE.” And, “Really? Your business plan…is so tied in to free ads on CL that you’re blaming the flagging of your ads on having to let go employees? I’m stunned.”

Nascimento is hardly the only complainer. There are scores online. “It’s always the same,” he says. “Just the names are changed.”

Take this cry for help on Yahoo! Answers. “My competitor is flagging me mercilessly on Craigslist.… How can I fight back? I own a small mattress company and pay someone to run it for me. My main competitor is a larger company.… When I started, I’d post 3, maybe 4, ads daily, but he would flag them all. I know it’s him because my best friend works for him and has told me that he does flag all my ads, so I’m 100% sure it’s him. He will post 40 to 50 ads daily. This is not an exaggeration, I counted. Some days I’ll post 15 to 20 ads just to get up there but my competitor will flag them all down.… One night I stayed up and posted 10 ads. They all stuck. By 9 o’clock in the morning they were all gone.

“How on earth is he doing this?

“I’ve tried everything to stay up there but he flags every single one of them down every day and I can never take down any of his. I’m not trying to put anybody out of business or damage somebody’s business. I’m happy sharing the pie with everybody. But this guy is literally taking food off of my table by doing what he’s doing. In the beginning I tried to fight the good fight and just post more ads and not flag his…two wrongs don’t make a right, right? The more I posted the more he flagged and now I’m probably less than 3 months from going under.… I’m not one to do something like this but he’s not going to stop until I’m out of business. Can somebody please tell me how to flag this guy so he stops flagging me?”

Nascimento invites me to place the simplest ad I can think of in Craigslist’s computer “Services” section. “It’ll be gone in 10 minutes,” he says. “You watch.” So we place an ad with a generic promise to help “with your computer problems at a reasonable rate.” Then we wait. At about the 20-minute mark, Nascimento says, “This reminds me of going to the doctor for a pain that doesn’t hurt once you get there.” But sure enough, just as we are leaving, the ad is deleted. Since it takes a number of flags (no one is sure how many) to prompt Craigslist to delete, I wonder how it can happen so fast.

“These companies that are flagging off their competition have to be hiring somebody to do it,” Nascimento says. “If I, the little guy, spend all my time reposting, then I can’t get anything else accomplished. Obviously, I don’t want to do that. But the bigger guys? They just pay somebody to watch Craigslist all day long and do the flagging.”

Still, there have to be a number of flaggers, right?

Nascimento calls my attention to 16 YouTube videos that explain how it’s done. Craigslist determines whether flags are coming from different sources, he says, by automatically monitoring their internet protocol numbers. “So all the bad guys do,” says Nascimento, “is keep changing one number in their [internet protocol] identities before they flag. That’s what one video tells you how to do.”

When I bring up the first video, which is oriented to the real estate industry, the narrator is talking about “the ultimate in the art of war. I’m going to show you,” he says, “how to dominate your Craigslist market.” The technique relies on the use of “proxy” internet addresses that prevent Craigslist from seeing that the flags are coming from one location only. This “Craigslist flagging tool” allows you to have new flags, close to 50 of them, sent from a different address every ten seconds.

But the video Nascimento wants me most to see, called “How to Flag Unlimited Craigslist Ads,” advises against the use of proxies. “They suck,” the new narrator says. “They’re too hard to find.” What he describes instead is a multistep method, using a number of software tools, of changing your internet protocol number. He admits that what he is doing is controversial. Some people will see it as only helping the crooks put more people out of business. But he feels that he must blow up the phenomenon. If enough people start doing it, he believes, Craigslist will finally have to take steps to control the flagging that is making a joke of its free service.

“It would be easy,” says Nascimento. “All Craigslist would have to do is charge a dollar for each ad. I’d pay it, no problem. Then they could afford to hire company moderators of all the flagging that takes place on their site. They know exactly what’s going on. After wiping out so many advertising sellers by now, they need to be responsible. Originally, we all thought Craigslist was a hero, standing up for the little guy. But now the big guys have turned everything around, and Craigslist doesn’t care.”

As of this writing, Craigslist has not responded to my questions about what, if anything, they are doing to address the situation.