http://blog.searchenginewatch.com/blog/060313-090116

Analyzing the SERPs of the last few updates, it appears that the latest algos do not just calculate backlink anchor text as it once did it is calculating anchor shards. Of course TrustRank, Popularity of Links and Theme of backlinked Site are also increasing in algo-importance.

There have also been sudden simultaneous temporary drops across datacenters for a particular phrase – while the the equally competative others are still ranked – although the same backlink quality exists, as well as certain anchor text ranking high by themselves but dropping severely when combined with other ranked phrases for the same sites.

It appears that the anchor phrase go through a constant correlation reprocessing with Google's pre-existing Shards to regenerate rankings.

It appears now more than ever, the keyprhrases in the anchors will have a tremendous effect as opposed to the keyword emphasis of previous years.

This may require varying the backlink anchor text in any link exchanges – and using the phrases as they wouldl be queried by searchers.

Again, this is only an interpretation – perhaps others have a different analysis

I have seen many websites, where the "Shards" concept works...

This post on SEW is from Mar. 13, 2006...