I can see why Apple don't want multiple user accounts - they'd prefer that families didn't share one iPad, etc.
But they do need a guest account feature similar to the one in OS X. People are always asking to check their mail/Facebook/whatever on my iphone. The problem is that I'm permanently signed into my work email, Twitter and Facebook accounts, not to mention Safari, photos, banking apps, Messages, a journaling app, etc. It's not that I don't trust people, but it would sure be nice and convenient to just have a guest mode.