I noticed some Pro bloggers moaning about PR drop on their sites. Problogger.net which is the king pin of the B5 Media network dropped from PR7 down to PR4. They rely heavily on paid sponsor Ads and these sponsors use PR to evaluate the value of an Ad placement. No wonder the Pro Bloggers are annoyed 

Actually, they are a bit dumb since big G has said all along in their terms and conditions that artificial linking schemes are not acceptable. These blog networks interlink between blogs of unrelated subject matter and regularly blog about each others posts so it is no wonder that they got de-ranked IMHO.

What we can learn from this is that it is good to link out to other sites that help our readers get more info on what we are talking about and these other sites are not always a part of our closed little network.