Actually, Poser doesn't assume it has infinite memory...or at least it doesn't consistently. At the very least, it is held hostage by the 32 bit limit.

And Diolma, I'd have to disagree that every app should handle it's own memory management. For starters, very few people can do more than basic memory management well. There's no such thing as "fairly simple" memory management in anything but the most trivial teaching examples, and if your memory management needs are that simple, you're better off getting lumped in with the rest of the OS's memory management so that it can be smart about fragmentation and swapping. It isn't like you can isolate yourself from the memory use in the rest of the system anyway, and if you could, then you'd be a very badly behaved app to do so.