The 25 most media-prominent think tanks were cited 17 percent less in 2007 than they were the year before, FAIR’s annual survey of think tank citations found. The decline was felt across the board among centrist, conservative and progressive think tanks.
Researchers were somewhat baffled by this finding, but I can speak for my small part in the phenomenon: The difficulty of trying to find just the right quickie descriptor (right-of-center? progressive? wingnut? moonbat?) combined with the fact that many think tankers also have a university affiliation makes it desirable to just drop any mention of the tank tank altogether wherever possible.
Academics like Tim Groseclose and Jeff Milyo have used media citations of think tanks to take a stab at quantifying media bias. Their study makes me (and likely other journalists as well) much more aware of when and how to cite think tanks, and more likely to use a workaround where possible. It's worth noting though, that I'm a backstabber--I still find sources through think tanks, I just don't cite them as such if I can help it. Lack of citations may not indicate the the influence of think tanks is actually, well, tanking.
Via Jacob Grier