I wrote a post a few years ago that made the digg and reddit homepage saying Experts Exchange should be removed from Google’s search results because they were using a technique called cloaking - hiding their content behind registration and showing a different version of their pages to the Google crawler.
Google just released a Chrome extension to blacklist sites from your search results. Part of the functionality includes sending the blocked site back to Google - which might eventually have some impact down the line on search results.
I’ve already blocked ehow and experts exchange. It’s a fantastic day for me. Check it out here.