Here’s how they do it:
We scan several million blogs a day to see which online videos people are talking about the most. We count the number of times each video is linked to and the number of times each video is embedded. Every morning, after we’ve had a cup of coffee, we publish a list of the 25 videos that generated the most buzz over the previous day. We reckon this is a pretty good yardstick of what’s hot and what’s not. At the moment we only look for references to videos on the three most influential video sharing sites: YouTube, Google Video and MySpace. We tried looking for references to videos on some other sites for a while, but nothing ever made the top 25 so we stopped.