Yeah, I was pretty incredulous when I first discovered over-commit in Linux - I asked for memory and you gave it to me without an error, and now that I am deep in the guts of processing and can't easily recover, now you decide to tell me you don't really have it!

But once you know about over-commit there are workarounds in languages where you control memory allocation, like touching every page right after you allocate it, but before using it. And in a garbage collected language you don't have any control or insight into when OOM exceptions will occur in either approach. So the ability for the OS to not trust lazy and greedy software that asks for memory but doesn't use it seems like a reasonable trade-off.