I'm curious what effects libraries have seen from their MySpace pages. I'm interested more in the direct, measurable impacts -- the "X people came to this program that they learned about on our MySpace page" -- than the general "We're reaching users and potential users on MySpace". (Not that I'm dismissing the value of simply having a presence -- positive effects often aren't immediately quantifiable; I just feel that that particular topic has been reasonably well canvassed.)
I'll admit that my one (non-work-related) attempt to use MySpace as a promotional tool didn't have much of an impact despite a pretty heavy amount of effort. I'd love to hear success stories, however.