tedster - 7:22 pm on Feb 28, 2011 (gmt 0)
Here's the methodology behind that Systrix data. They monitor 1,000,000 high traffic keywords. They took US rankings the day before (Feb 22) and the day after (Feb 24) the new algorithm rolled out.
This list is the top 300 sites who lost the most keyword positions. It is total positions lost, not weighted by potential traffic loss.
The 300 list is worth a study, IMO, even without any traffic weight in the stats. Losers include prnewswire, autobytel, daniweb - that's quite a diverse group.