Hamilton had lost the place, and clearly could've backed off and avoided the accident, HOWEVER Grosjean (black car) also very sharply moves right into him before he has completed the pass. Grosjean admitted afterwards he thought he was past Hamilton before he moved over on him.

As much as Hamilton COULD have avoided it, he is under no obligation to let a car pass him unless he is being told by the race stewards to do so (eg blue flag). He also couldn't have predicted the sharp right turn. If Grosjean held his line it wouldn't have happened.

I disagree with enclosed cockpits in F1, but it could provide added safety. Fortunately it's been 18 years since the last F1 fatality, and even injuries are pretty rare. It does make you think about what would've happened if Alonso (Ferrari) was about 30cm closer to the Lotus flying past (and 30cm is nothing in F1, you couldn't blink at that speed).