I like Ryans idea about displaying location. I had read somewhere on the site that BPL were looking at the idea of creating User Profiles and I guess Town, State, Country could be linked into that. It might be kind of cool to have a user profile with space for a bit about yourself, your current kit list, favourite gear etc. However, the security point raised above is valid and therefore it should be optional instead of compulsory.
Just so you all know, I live in Luton, Bedfordshire in the UK. For those who don't live in the UK, it's a town of just under 200,000 people just 30 miles north of London. However, I live right next to open countryside (Only 60 seconds walk away).
It would be good to see BPL related users getting together in their own part of the world, where they choose to do so.