Rendezvous + WiFi + FOAF = People in my Neighbourhood

If you had a bit longer range then Bluetooth (30 feet is kind of short, 100-150 feet would be just about right, IMHO), and some reasonably standard way of mapping device IDs to people (think FOAF or something Technorati- or Google-driven, where people opt-in by posting their own IDs), and we could have a really fascinating way of building communities. There are certainly a ton of privacy issues, but those could be mostly mitigated by the opt-in nature of the device ID→identity mapping and by turning off Bluetooth discovery on your phone. *scottstuff*: Bluetooth Jabberwocky

Mmmm...what about Rendezvous + WiFI, and using the MAC address of your WiFi card?