Phil, one big difference being that if Massa gave room, he would have hit Webber.
Look at the Youtube feed (that I linked further up of the incident). Massa did indeed get too close to Webber in the following up of the corner, which Hamilton used as his opportunity to overtake, as Massa left his inside wide open and would have to brake accoardingly because of traffic ahaed. Massa didn't pull in early to not hit Webber - he pulled in early
because Hamilton was coming up his inside. By closing the radius earlier, he effectively got even closer to Webber at an angle (shorter distance traveled) which resulted in him colliding with his front-wing. You can see this if you especially compare this to the previous laps (laps 32/33) where Massa is also held up in those corners, but sticks to the normal racing line with a late turn in.
In this, or the Maldonavo incident, Hamilton was clearly commited to his move. Massa did not yield and turned in, despite seeing Hamilton being next to him. I'm not sure what Massa expected - that Hamilton just disapears? At that point, keep in mind, Hamilton was traveling faster and we can assume was full on the brakes already as to not overshoot the corner.
In the Maldonavo incident it's the same. Hamilton commited himself to the overtake from before the start/finish line. It's the DRS zone - Maldonavo knew fair well that Hamilton was coming. Forgetting for a moment that this is Monaco here - even on a normal track, you are allowed to do your one-move block - to force the overtaker either to chose the inside or the outside line. Once you're commited to your line though, you can't simply turn into the apex of a corner if there's a car beside you. That surely will end in tears.
As I said, I'm not arguing that the moves weren't risky or faultless. In Monaco, no move isn't. It takes two for a successful overtake and I think just as you can expect team-mates to give room, you can also expect rivals to give room. If you don't, don't expect to be entirely faultless.