At first I thought it was 100% Maldonado's fault. Now, after watching this multiple times I'm not so sure.
http://www.youtube.com/watch?v=uxf0l8lsSUI
Most of the corner they are even, that's true. In the end though Maldonado is just enough ahead to ''claim'' the corner. However, I don't think Maldonado believed for a second that he could claim the entire corner he just came too fast and couldn't do a thing than just keep going and hope Maldonado cedes.
Grosjean could've seen the situation early and let go but instead tried to maintain his position too long, even when it was evident he couldn't win. Once he runs out of track he turns right and actually hits Maldonado - not the other way around. He could've just went to grass and lost time but chose to ram Maldonado hoping he'd survive.
To summarize: Maldonado came too fast, but Grosjean could've prevented the crash by smart driving. Both are partially at fault and it is a racing incident. There was no penalty since Maldonado didn't cause and ''unavoidable accident''.
To add: I don't like Maldonado one bit, the way he commented about the crash ("It was a clean one. There was very little contact – very little, not enough to put him out.") was just ridiculous and shows he didn't bother seeing the replay and doesn't care what happened. That's not professional at all.