Bandcamp is a simple and brilliant site. This is no surprise, and I give it full props for being one of my favorite streaming sites. (Would be my absolute favorite if it had a larger database, but that's a band's prerogative, not the site's.)
bandcamp is the best. then soundcloud. turntable.fm was cool for a few months, then everyone i know stopped going on it. spotify can go fuck itself because i can't get it work. last.fm sucks if you don't have an ipod, but i like to use it on my xbox. never used tunecore.
If it were between iTunes and Bandcamp, it'd be Bandcamp all the way. One reason: .flac files.
Essentially this. There's been many many many times where I was about to go buy a CD off of Amazon or the artist's site, then said, "Wait, let's see if this band has a Bandcamp profile." It's the best way for anybody to buy music.