Interesting. Theoretically it seems possible.
Linux normally has 2 users: root and a user, on Maemo you're named user.
If you made a second user, f. ex. guest, that user would not have access to the files on user, because if the user user has a password or is an account with a higher priority, the guest cant access it.
So, theoretically, yes, if you can enable the user-system, or if you can implement an ARM-based user-system.
Note: This is only theory.