The claimed subject matter relates to an architecture that can mitigate privacy concerns in connection with ad targeting or data collection. In particular, architecture can be included in a personal mobile communication device such as a cell phone. During communication transactions between the host device and a peer device, shared information can be extracted either from content included in the communication or from metadata. Based upon the shared information, a social graph maintained on the host device can be updated. In addition, the host device can receive a large set of ads and select or tailor a custom ad from the set based upon the social graph.