One of the notable features announced with the release of Android 4.2 yesterday was support for multiple users on a single Android device. Google's list of 4.2 features, though, makes it very clear that multiple users is supported only on Android 4.2 tablets, not phones.

TechCrunch speculates that the limitation is due to a patent—US 2005/0107114 A1, "Multi-user mobile telephone," to be specific. The patent was filed in late 2004, granted in 2005, and was penned by then-current Symbian employee Tim O'Cock. The abstract makes it pretty clear that it envisions several different people, each with their own personalizations, using a single device:

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; 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 USPTO lists the patent's current assignment with both Tim O'Cock and Symbian Limited, with both pointed back to Nokia. TechCrunch guesses that the original intent behind the patent was to take revenue from emerging markets by providing an easy method for lots of different folks to share a single phone; in areas of the world where cellular phones are expensive, a feature which lets several people use the same phone gives that phone a competitive advantage.

It's easy to see how this patent might be a potential stumbling block to any company wanting to implement a similar feature. The patent language is broad enough to cover just about any possible implementation of multiple user accounts, and even though no Nokia phone has shown up with anything like "multiple users" on the feature list, anyone with something similar in mind would have to deal with licensing from Nokia.

The loophole which Google is using to bring the feature to tablets is that the patent language very clearly states "mobile telephone" over and over again. In 2004 when the application was filed, consumer-grade tablet devices were but a twinkle in technologists' eyes (stylus-driven "tablet" notebook computers notwithstanding). The patent narrowly applies to phones, not "mobile communications devices" or anything else.

However, the "freedom to tinker" mindset which pervades the Android ecosystem might win out here. If the feature is available in tablets, it is likely only a matter of time before enterprising Android 4.2 hackers (and I mean hackers in the good sense of the word) find a way to enable the functionality on their handsets.