A couple of weeks ago there was a thread discussing the hyphen (-) and underscore (_) characters and how Google treats them. There are also various other threads discussing the same thing (site search on "underscore hyphen google").
My understanding of the end result was that hyphens are treated as spaces (or word separators) but underscores are not:
If this is the case then how does a search on "Brett" (http://www.webmasterworld.com/forum3/13907-1-15.htm) match his profile page which only contains the word "Brett" as part of the substring "Brett_Tabke"?
Is this a case of inbound link text creating the association between the two terms? Not from what I can see.