Remove Spam from Google Blog Search Google Operating System (Oct 22)
Names two features Google Blog Search has to reduce the number of splogs (spam blogs) from search results.
+ a duplicate filter that removes nearly identical posts (most of the time)
+ option to sort results by relevancy - get the benefit of other weighting factors.
Other ideas:
+ exclude blogspot.com and the .info domaiin because of the amount of spam there
+ exclude Google Alerts because of misuse at blogs.