Whitey - 1:54 am on Apr 26, 2012 (gmt 0)
The anchor text thing is something that I believe was tweaked a month ago, more or less. I suspect this is something else.
There was a large scale drop around 3 weeks ago for those with paid links on detectable networks. I don't think this had anything to do with "exact match" or "over optimization" caused by the same type of link spam.
But i acknowledge seeing some downward movement earlier on core terms created through excessive exact match anchor text link tactics, which has now accelerated - so yes, it could have been part of the overall algo change that came recently.
This algo tweak seems to have permutations of excessive "exact match" tactics all over it. The answer is probably diversification and removal of all offending links. Link brokers will be misleading folks if they continue to peddle this garbage service.
The problem is that it appears to lock sites with links created many years ago, which will make large scale campaigns difficult to reverse on some dates. If sites have not engaged in this garbage linking for many different good reasons e.g. domain / site acquistion and have focused on clean freely given links for many years, then it would seem unfair to hold them to account after so many years for preceding failures. It would be better depricate the old links and permit new and diversified links in.
There are reports on some threads that new links have not been sufficiently rewarded, but more and better inputs should clarify this.