Last year, Gawker Media took a big step in stemming the tide of bad commenters on their media properties by introducing tiered commenting.
Nieman Journalism Lab provides a thorough write-up of their experiment. From the article:
“In essence, Gawker’s ‘class system’ means unknown commenters get stuck behind a ‘show all discussions’ link few users will click. What most readers will see are only the musings of trusted commenters and the few comments from the riff-raff that either Gawker staff or trusted commenters have decided to promote.”
Tom Plunkett, Gawker Media’s CTO posted a chart of the comment growth on his site. Notice the immediate dropoff in comments after the new implementation followed by a powerful rebound.