Jon Stewart Follow-up

New York Times article on the Jon Stewart-CNN exchange:
http://www.nytimes.com/2004/10/24/weekinreview/24cave.html?8hpib
Discusses whether or not Jon Stewart should be asking tougher questions considering he attracts a larger audience of 18-34 year olds than network news.

In this article they quote a blog, a reoccuring theme in many of the articles in the Times. But, is quoting something someone wrote on a blog a valid source? From a reporter perspective its definitely time saving and cost-effective but is this journalism? I raise this question because of the still potentially anonymous nature of blogging- how do I know that the blog posting I'm quoting is legitimate and from the person it says it is from?

Don