It appears Letterman isn't a fan. Here's some cute banter with Kevin Spacey, about Twitter (and it's cost):
Oh, what's that? The fail whale image above isn't a Letterman clip? Oh, right. Due to an epic YouTube FAIL, the video was way too wide for my blog, and as a result, cut off about in the middle (perhaps this is a blog FAIL? No, I think this is a YouTube FAIL). Go here to see the version that is too wide for this space.