A research paper for USENIX, “TaintDroid: An Information-Flow Tracking System for Realtime Privacy Monitoring on Smartphones”, accuses android applications of leaking information without user approval.

Using TaintDroid to monitor the behavior of 30 popular third-party Android applications, we found 68 instances of potential misuse of users’ private information across 20 applications

Fifteen of the apps sent user data to advertising companies without user approval or notice, while other apps sent unique IDs and tracking/location data (even when the application did not run).