Who Uses Fact Checkers, Anyway? is an interesting article worth noting in the context of blogging, especially given its inherent emphasis on timeliness in posting content. For some "historical" context, see this 1999 article from Searcher, Fact-Checking 101. (Forbes Magazine's information center), which provides some much needed perspective on the limitations of virtual libraries, and the demand for instant answers when the situation may demand more time to analyse and determine the appropriate response or answer.
And from Jim Tyre, this link a memo (in pdf) that he would give to new attorneys/law clerks.