This will allow parents to lock certain apps behind a password so that their kids don’t get access to anything that is deemed inappropriate. Those who wish to share their phones will be able to do so without worrying about what another person may access.
The feature was implemented on tablets in 2013, but will soon make its way to phones. A Google employee confirmed in a thread on the Android issue tracker that the development team has implemented the feature for phones. They said that “it will be available as a part of the next public build.”
Unfortunately, the employee didn’t get any more specific than that. So, we’re still unsure when the multiple user account feature will be implemented. However, for those who share their phone, it is a welcome piece of news.