I recently lost my PR in the last Google update, and went from 2 to 0. I realize that it was due to not following certain Google rules, specifically about adding the nofollow tag to paid links/reviews... I did that, and applied for reconsideration.... Google gave me back my PR2 but no more. However, I noticed that although I got my PR back, traffic was still lower than normal, and I got search engine traffic for weird words not the main keywords I used to get traffic for before. I investigated more, and discovered something strange: All of my backlinks now have PR0! I had backlinks ranging from PR0 To PR5.... lots of PR1, PR2 and PR3s... now all are zero. Does that have something to do with the new update?... no way all of these sites got deranked.
If the links are all from sites that Google thinks are selling links, that would explain it. Most directories have gone to PR0.
Probably these sites were also selling links. Google noticed it and cut their PR. As simple as that. Go for informative, useful content wherever you can afford it and good (PR, relevant) backlinks will come. When you can't build backlinks this way use another techniques but, as you already know, you can't fully rely on bought or spammy backlinks because future of pages serving this is not sure.
if you take 5 minutes and write down everything you're doing write and then everything you know you're doing wrong (link exchanges are not google friendly) you'll see why google is penalizing you. just write good content, play by the rules and your PR will go higher than 2 with time.
Actually my first site had PR higher than 2 (PR4)... that was long time ago. I started doing *nasty stuff* and google gave it PR0... Now with my new site, they only gave me PR2 and are sticking to it.... each update it is still PR2 although I'm building links properly. It was when I gave up and decided to start ignoring some rules, that they immediately gave me PR0.... after reconsideration request and fixing the issues, they gave me back PR2 (3 or 4 days after reconsideration request). Also I have many backlinks from sites that are doing white hat seo... it can't be that they are doing some blackhat seo or non google-friendly biz, that they penalized them! I had PR5 backlinks from other sites, even from here, DP... now the pages are PR0 !? WTF?!
But you bought these links right? Or did they came naturally to you from white-hat-google-friendly-biz-running-sites? Maybe these sites also sold links to other people, if Google acknowledged it PR of these sites was to drop quickly.
No, I didn't buy links. I don't know if these sites are selling links or not, but I can't believe ALL of them are doing so... how about the backlinks from here, DP?