DIRECTION OF THE MASHUP

Not long ago, Google released the “My Location” functionality in Google Maps Mobile, which allows you to see your location on the map regardless of whether or not your phone has GPS support. At the moment this adds limited benefit due to the accuracy (or lack of), but does raise a LOT of interesting questions, particularly in relation to a social networking/mobile/mapping mashup. Imagine being able to see the location of your facebook friends that are within a 5km radius…
Taking this idea a couple of steps further: imagine being able to find people in your area looking for a game of tennis? Or using a dating service that shows everyone nearby who’s looking for a date?
This all sounds quite cool, but begs the questions: do I really want to know that my partner is looking for a date in the city? Or that my friends have all gathered together without me?
I’m a strong advocate of open information, but this one has me stumped. I’d be interested to hear other opinions on the matter, how your privacy could be protected, or even just some fun/interesting applications of the concept.