Similar to Apple’s iTunes program, Google Music only allows a certain number of devices to be connected to the service at one time. Google allows users to upload up to 20,000 song for free, which can then be accessed by up to 10 “authorized” devices. Once the limit is reached, a user can “deauthorize” a device to allow another a different phone or tablet to take its place. The problem, however, is that Google has limited device deauthorizations to just four per year. While Google’s limit may not affect the average Joe, rooters, ROMers, enthusiasts and even bloggers may run into some trouble. Custom ROM users in particular may run into trouble — Google Music often has difficulties handling custom ROMs and will occasionally de-register and re-register it as a completely new device. According to XDA-Developers, the change is relatively new, and was rolled out over the last 60 days.
UPDATE: Google issued the following statement regarding the policy change. “We limit the number of times you can swap out new devices at the request of some of our music partners in an effort to limit abuse. We understand this has caused some issues for users who often deauthorize and reauthorize the same device, and we are currently re-implementing the solution in a way that works for our users and music partners.”