The vast, relatively unregulated territory of the Web, like the Old West, is proving hospitable to such Lone Rangers with their own ideas of justice. “One aspect of the Internet is that law doesn’t reach it all,” says John Palfrey, a Harvard Law School professor who specializes in privacy and technology issues. “It’s hard to police. So you see private sheriffs popping up all over the Internet—private actors taking law into their own hands because no one’s policing it.”

“Some people call it cruelty,” Crook says as he doctors up a photo of some grinning brunette he’s downloaded to use in one of his fake ads. “I call it accountability.”

Crook’s degree of vindictiveness may be singular, but he’s just one copycat following the spontaneous—and booming—trend of online sex-baiting. It all started last September, when Jason Fortuny, a 30-year-old graphic designer in Seattle, put up a phony ad on Craigslist, posing as a submissive woman looking for an aggressive, dominating man. He got 178 responses, each of which he posted on the Internet: phone numbers, cock shots, and all. A few weeks later, Crook gave it a go too, taking it several steps further. Then a 24-year-old Portland, Oregon, resident posted an ad as a 26-year-old woman into bondage, collecting the hundreds of responses he got and uploading many of the sordid details onto a public site.

Why would anyone do this? Crook has no qualms about his actions. “Sure, these guys didn’t break the law,” he says, “but isn’t it kind of pathetic that they’re looking for sex on Craigslist?” (He’s married—he met his wife not online but at a church dance—and the father of a 2-year-old daughter.) What might speak louder as a motive, though, is Crook’s history of provoking rage as a hobby. His home page contains a link to a Holocaust-denial site, and he’s argued that American troops deserve to die for enlisting—that they are overpaid “pukes” and “scumbags.” He’s purchased the URL for a future project. It’s not hard to see his sex-baiting antics as a blend of sanctimonious policing and attention-grabbing stunt.

“Have you thought this out?” one of his victims, who calls himself Paul, wrote in an e-mail to Crook. “You are in the process of ruining lives. . . . This is no frat house joke. If you were to lose your wife, family, friends and job, consider what a man might do. . . . My advice, take it down before it gets out of control and I’ll consider it a good prank. Keep it posted, live in fear.” Crook cut and pasted Paul’s e-mail, in its entirety, onto his website.

Not all sex-baiting has ethical overtones, though—purported or otherwise. Some make no excuses for its intent: to cause grief to anyone foolish enough to handle his personal information carelessly. Fortuny, who started the phenomenon, might be considered a distant cousin of a “griefer” (in Net lingo, someone who kills teammates in online multiplayer games) or a “troll” (someone who revels in making others miserable by, say, dropping the n-bomb in black-rights chat rooms). He’s mostly interested in taunting those who he feels take themselves seriously. Fortuny’s venture into sex-baiting, he says, was an experiment. All he did was cut and paste someone’s Craigslist ad from another city—“it drives me krazy 2 get tit fucked, cuffed, ass spanked with welts and bruises”—and post it in Seattle.