Google Pagerank changes

Probably, you have read lots of posts in this period related to pagerank changes that Google has made. Google has updated, this month, two time the pagerank...and lots of sites have seen their value drop off (normal everyone has lost 2 points). And also my blog has received the same treatment. I don't know if Google has penalized sites that sell links, have ads or something like this...I just know (thanks to this article of DailyBlogTips) that some very important sites have been penalized: Engadget (from 7 to 5) AutoBlog (from 6 to 4) Problogger (from 6 to 4) Copyblogger (from 6 to 4) Search Engine Journal (from 7 to 4) Quick Online Tips (from 6 to 3) Search Engine Roundtable (from 7 to 4) Blog Herald (from 6 to 4) Weblog Tools Collection (from 6 to 4) JohnTP (from 6 to 4) Coolest Gadgets (from 5 to 3) CyberNet News (from 6 to 4) Washington Post (from 7 to 5) Washington Times (from 6 to 4) Charlotte Observer (from 6 to 4) Forbes.com (from 7 to 5) SFGate.com (from 7 to 5) Sun Times (from 7 to 5) New Scientist (from 7 to 5) Seattle Times (from 6 to 4) Hongkiat (from 5 to 3) Sabahan (from 5 to 3) And surely other sites will be added!