Maintaining the security and privacy hygiene of mobile apps is a critical challenge. Unfortunately, no program analysis algorithm can determine that an application is "secure" or "malware-free." For example, if an application records audio during a phone call, it may be malware. However, the user may want to use such an application to record phone calls for archival and benign purposes. A key challenge for automated program analysis tools is determining whether or not that behavior is actually desired by the user (i.e., user expectation). This talk presents recent research progress in exploring user expectations in mobile app security.