Jailbreak would be your best option for something like that.
iOS products are designed for a single-user experience, not to say multiple people can't use it, there's just no log in or anything like that for any iOS device.
BUT that only applies to iDevices running Apple's software.
As stated before, there's a huge chance that some jailbreak is out to allow multiple logins or something to that effect on a jailbroken device. Now I can't say for a fact that a jailbreak offers this, but I'm going to trust that their most likely is.
I would look to the jailbreaking threads and maybe look around there if you're interested in the jailbreak option.