tedster - 1:37 pm on Sep 15, 2011 (gmt 0)

The data on blocked sites probably helps to confirm or reinforce what the "short click" data already seemed to indicate.

I'm pretty confident that Google has been using "short click" and "long click" data for a long time. Now, since logged-in users get an option to block the site after a short click, that helps to eliminate some of the noisiness in the short click signal.