You don't need to believe that blogs killed Paul Tilley to agree that there is such a thing as "too far," and that many anonymous Web comments go there. But what's to stop them?

Not the law—at least not for now. Section 230 of the Communications Decency Act, passed in 1996, ensures that website operators and internet-service providers can't be prosecuted for libelous or otherwise unlawful statements generated by third parties (although the third parties themselves can still be held liable, provided they can be identified).

In fact, Section 230 was originally written with the intention of cleaning up the Web, according to Thomas Burke, a partner in the San Francisco law firm David Wright Tremaine, who specializes in First Amendment law.

Prior to the passage of Section 230, internet companies feared that by editing or censoring comments, they were acting as publishers of the comments, thus sacrificing what's known as "conduit immunity." Section 230 allowed them to make "good faith" efforts to exercise some control without incurring liability.

"Of course, in practice it didn't work out that way," says Burke. "A lot of sites said, 'Well, we have immunity, so we're not going to do a thing.'" Still, he says, the courts have "with very few exceptions held that Web owners are not responsible and have immunity for content and comments posted by third parties, period."

Yet it's possible to see the legal consensus shifting as the line between first-party and third-party content fades. No one has done more to blur this line than Gawker Media, which regularly highlights the best comments and reader-suggested captions, selected by editors, in space normally reserved for editorial writing; invites readers to contribute their knowledge to developing stories; and hosts discussions between writers and readers in the comments section.

Gawker has also hired exceptional commenters to write for the site, and recently gave commenters the capability to embed video clips in their comments, in effect turning them into mini-blog posts.

It's obvious why Gawker puts so much energy into cultivating its commenters: Because they click on the same item over and over, comment traffic grows at an exponential rate. Gawker Media's traffic doubled between February 2007 and February 2008, but its volume of comments quadrupled, says owner Nick Denton.

These kinds of tactics could put blog operators at risk of forfeiting their Section 230 protection, says Jonathan Kirsch, a publishing and intellectual-property attorney based in Los Angeles.

"There is a threshold you cross as the editor and publisher and operator of a blog where [third-party content] is no longer immunized, because in a sense you've adopted it by selecting it out and featuring it," he says.