HeyYou is a peer-to-peer social app that works over WIFI. It discovers all other users on the local network and allows messaging, sharing photos and adding contact infomation. It was designed for two distinct situations: Conventions where lots of business cards are exchanged (I hate business cards), and the local club/bar/coffee shop where you can start a conversation.
Since communication is restricted to the local WIFI everyone that is found is right there nearby. No information is sent to a server so there are no privacy issues. Only the information that you choose to share is made available, and only then after you grant permission.