What follows is a going to be pretty controversial and I don't have hard numbers to back it up, but my instinct tells me it is true.  Blogging will ruin Google's PageRank algorithm.  Bloggers are highly clustered group with unusually large number of interlinks between each blogs.  Bloggers also tend to cover pretty wide variety of topics.  Google was not designed with the rise of blogging in mind.  I predict that blog sites will rank high in almost all topics in the near future, rendering Google useless unless blog pages are treated differently.