Behave Google conform or take a hit

Today Google penalized a few link and blog networks as well as some trusted sources. One of the ones that took a heavy hit is Statcounter, a well-known counter service from Ireland. Their Pagerank dropped from 10 down to 6. Also all of these sites seem to have lost some PR: http://www.autoblog.com/ PR6 PR4 http://www.engadget.com/ PR7 PR5 http://www.problogger.net/ PR6 PR4 http://www.copyblogger.com/ PR6 PR4 http://www.joystiq.com/ PR6 PR4 http://www.tuaw.com/ PR6 PR4

http://www.Forbes.com PR7 PR5 http://www.sfgate.com PR7 PR5 http://www.washingtonpost.com PR7 PR5

So what's the reason for this?

I strongly believe it has to do with link selling or extreme interlinking. From the last three "trusted" sources, I know for fact, that one of them is a big link seller.

Does this make them a bad source of content?

Of course not, but I hope the screaming won't be too loud. It's the PR, that nobody cares about anyways and all the webmasters knew that this was coming. I believe this is just the first round of "cleaning" the index and it is the yearly warning to webmasters in order to make everybody behave "Google-conform".

If this is an effective method to get the masses out of link buying networks is a question I cannot answer. But what I can tell for sure is that "real" SEOs know how to buy or attract links below Google's radar.

Update:

Also Etracker.com took a hit from PR9 to PR5.  Etracker is also a link seller, but selling links, that don't count for SEO. So I assume it's the nature of free web analytics tools (that back link to the software), which were penalized.