Android device ID potential risk?

I am using this code to obtain the device ID:

TelephonyManager tManager = (TelephonyManager)myActivity.getSystemService(Context.TELEPHONY_SERVICE);
String uid = tManager.getDeviceId();开发者_运维百科

I want to use this ID as a default login username, in order to make registration optional. Therefore, other users will be able to see other users IDs.

Can this be a potential security risk for users?

There's always some risk with using a default username. The concern I have for you is trying to identify a device with getDeviceId. There are a lot of concerns using that method to identify a device, such as non-phone android devices asking for a device id, bugs associated with getDeviceId, etc. Please see the link for a full detailed report.

http://android-developers.blogspot.com/2011/03/identifying-app-installations.html

After reading the report and weighing the drawbacks, it's up to you to decide whether or not you want to go with this method of identifying devices.