Not too long ago, theorists fretted that the Internet was a place where anonymity thrived.

Now, it seems, it is the place where anonymity dies.

A commuter in the New York area who verbally tangled with a conductor last Tuesday — and defended herself by asking “Do you know what schools I’ve been to and how well-educated I am?” — was publicly identified after a fellow rider posted a cellphone video of the encounter on YouTube. The woman, who had gone to N.Y.U., was ridiculed by a cadre of bloggers, one of whom termed it the latest episode of “Name and Shame on the Web.”

Women who were online pen pals of former Representative Anthony D. Weiner similarly learned how quickly Internet users can sniff out all the details of a person’s online life. So did the men who set fire to cars and looted stores in the wake of Vancouver’s Stanley Cup defeat last week when they were identified, tagged by acquaintances online.

The collective intelligence of the Internet’s two billion users, and the digital fingerprints that so many users leave on Web sites, combine to make it more and more likely that every embarrassing video, every intimate photo, and every indelicate e-mail is attributed to its source, whether that source wants it to be or not. This intelligence makes the public sphere more public than ever before and sometimes forces personal lives into public view.