I suppose the results vary from people to people, but Last.fm totally doesn't "push" corporation-bound music onto me. In fact, I think that's really beside the point; if the music you listen to is good, there shouldn't really be anything that would inhibit you from listening to it. Pure enjoyment is really what matters.
In a comparison with both Pandora and last.fm, I've found that they were pretty equally decent at picking out songs that I'd like to listen to. One irk that I get from Pandora is that it often tries to slap errant and somewhat irrelevant tracks on when starting a station for the first time and this continues until I press "I don't like this track." a couple of times. Last.fm does a better job for me when it comes to station relevancy, most of the songs I'd love appear first and foremost to me. However, after about an hour's worth of listening, tracks seem to taper off into irrelevancy until I just quit going through it and go through a different artist's station.
The two are pretty equally matched, really. It's just that last.fm is a lot more social-circle based and it also incorporates a lot of programs that can "scrobble" what you're listening to in media players in order to give you more recommendations based on what artists you like.