Oh yeah, definitely, if it becomes harder it also becomes more brittle. That's my understanding anyway, I could be wrong.

I don't believe it is anything to worry about though, ie. it won't become so brittle that dropping it or hitting it with a hammer will smash it.

It also depends on how much it has been bent. From the description given, it doesn't sound too bad. If you can see any "stretch marks" in the material near the bend, it may be too far gone.