Turbo, you have to stop thinking of Last.fm as a similar service to Pandora. It's not.
It's more of a social thing, where you see what your friends have listened to, what their top-playing artists and songs are, and even what they're listening to NOW. It's also a really interesting experiment in seeing what YOU listen to and how often. Its stat keeping is pretty cool.
Plus, if you find a friend that has a sufficiently HIGH compatibility in taste with you, you can scan through his/her favorite artists and those you don't know you'll probably really like.
Pandora is to sit back and listen, Last.fm is to poke around.