Thanks to the bright folks over at XDA-Devs, we now know a quick and easy way of turning multiple user accounts on, but keep in mind that this functionality is not yet ready for mass deployment, meaning that it will most-probably contain bugs and other such unpleasant stuff.
But enough talking, let's get right to enabling the feature!
HOW TO ENABLE MULTIPLE USER ACCOUNTS ON A JELLY BEAN DEVICE
1. First things first, if you want to enable multiple user accounts on your Android phone or tablet, you'll have to start by rooting your device, and then downloading the Terminal Emulator app from the Google Play Store.
2. Once you have the app installed, you need to launch it. When inside the app, you need to type and execute these two commands (without the quotes):
"pm create-user test"
3. Note that in the second command, "test" is the name of the new user that you are creating. Well, congrats, you have now created a new user on your Android device!
4. But that wouldn't mean much if you can't access it, right? Fortunately, you can! You simply have to hold down the power button, and right there at the bottom of the list you'll see "Primary" - your main account, and "test", which is the new user account.
5. Choosing the "test" option will send you to a brand new homescreen, which you can customize in an entirely different way from your primary one! Most info like photos, app info, music, contacts and Google Account will not be visible between accounts, but there might be some omissions that are not fixed by the Android team yet.
6. Repeat step 2 to create even more user accounts.
7. At some point or another, however, you may feel that you are self-sufficient and you no longer want multiple user accounts on your device. That's OK, because you can just as easily get rid of the additional accounts, by opening the Terminal Emulator app and executing the following commands (without the quotes):
"pm remove-user 1"
8. Note that in the second command, "1" is the second account on the device (or in other words, the first additional account that you've created), because your primary one is 0. If you have a third account, you just substitute "1" with "2" in the second command.
Coll stuff, eh? Just remember that the guys over at XDA warn that this functionality is not yet fully tested, so who knows what issues or bugs may hide beneath the surface.