The only problem that I can see with that suggestion is the speed at which the system would have to poll the individual users for location, then post those results to the end user. The inherent latency in such an operation would mean that in the time it takes for you to get the results of your search, the person probably moved on, anyway. It would also be quite taxing for the servers, resulting in much slower responses and longer load times for articles, forums, etc. Great concept, but almost impossible to implement efficiently.
demono69