I’ve set up a guest account on my Linux boxes using xguest. The Mac has a Guest account. I’m guessing most Windows machines do, too.
So why doesn’t the iPhone?
The iPhone is still enough of a curiosity and non-ubiquitous tool that people are always asking to look at it, use it, fondle it. I’m happy to oblige my friends, but I wish there were away to squirrel away my private data, open applications, and email. You know, a guest mode.
How about it, Apple?