http://labs.echonest.com/click/
I found this link quite by accident, and going back through my browsing history I can't even find out where I heard about it. Regardless, this is super-duper cool. Put in the name of an artist and a song, and it'll show you a tempo derivation map that will let you get an idea of whether or not it was played to a click track or not. That, in turn, can help you figure out some other things, such as whether the performance was captured or created (another cool link, but that's a recording blog I frequent). I love the comparison in that link, comparing and contrasting those ideas with photography vs. painting. It really is "art" either way.
For example, Britney Spears' cover of I Love Rock 'n Roll probably (definitely) uses a computerized drummer, vs. Joan Jett's original recording has alot of gentle push and pull.
And it's not that only heavily-doctored music has that sort of rigidness to the beat. Some of my favorite music I know for sure used a click track.
I like it this site. It's fun to play with. On a personal note, I do think it's important nowadays to play with a click - even just using a metronome in rehearsal is important for improved musicianship.