This BGR post is clamoring for mutiple account support for the iPad. Maybe all iOS devices including the iPhone and iPod touch. Well, you can forget about it. iOS devices are more personal than personal computers have ever been. This is probably the reason why Apple will unlikely ever offer multiple account support.
What Apple might offer one day is a sandbox feature that allows someone, say the owner's child, access to the iOS device when turned out and can only exit once the user's print or pass code is entered once the device is returned to the rightful owner.
That's as much as I see happening.
Today, smartphones and tablets are carried around by their owners. They're typically not shared at all. The husband has one. The wife probably has one. Maybe even the kid. Try prying that iPhone or iPad from their hands.
Besides, it's in Apple's self-interest that it gets its mobile devices into the hands as much individuals as possible. Sharing isn't something they really like to see or care for too much.
And let's say the author does eventually get this feature from Apple. Great, he got his wish and he's able to load differently profiles for use for his wife and children. How long before he goes out and buys each and everyone of his family member an iPad because they've been hogging his and he had not been able to use it?