Google recently unveiled Android 4.2 Jelly Bean along with the Google Nexus 4, Google Nexus 10 and new variants of the Google Nexus 7. One of the new features offered in the update is the ability for multi-user logins, which allows you to create multiple accounts on the device with various access rights for users. This feature is unfortunately restricted to Android tablets and wont be available on smartphones.
Multiple accounts can also be used in the situation of there being one tablet per household, allowing each user to have a separate account with their own app shortcuts, wallpapers and widgets. However this feature can also be used when you want to protect your personal files and messages when your sharing your tablet with your kid.
Since a tablet is not necessarily a personal device like a smartphone, we didn’t quite see the requirement for multiple accounts on a smartphone, but we do see the logic in wanting to protect your files from your kids. It turns out that Google intentionally left out this feature on smartphones and it may have something to do with a patent filed by Nokia back in May 2005.
A mobile telephone is designed to be used by several different end-users at different times. A first end-user can alter the mobile telephone so that it operates in a manner specific to that first end-user and a subsequent end-user can alter the mobile telephone so that it operates in a manner specific to that subsequent end-user; wherein each end-user has only to respond to prompts displayed on a screen in order to alter the mobile telephone so that it operates in a manner specific to that end-user... The present invention therefore moves away from the established assumption that a mobile telephone is personal to a single end-user and instead readily allows the mobile telephone to be used by several end-users through appropriate on-screen prompts. Such a device may be especially relevant to communities where few individuals can afford the cost of their own personal telephone. More generally, it is useful for any entity to whom there are benefits from being able to easily share mobile telephones across multiple end-users (e.g. large corporation may have a pool of such mobile telephones; any employee can then simply pick up one of these telephones and be able to use it like a personal device).So it would look like Nokia holds the patent to multi-user accounts on a smartphone and Google wants to avoid having to pay royalties to use it on their Android handsets. Microsoft on the other hands has a chance of taking advantage of this on Windows Phone 8 and we will likely see their recently introduced kids corner evolve into something more comprehensive over time.
source - TechCrunch