Similar concepts (i.e. connect to random strangers' devices when in close physical proximity, and trade mini profiles/trading tokens/whatever) have been done at least half a dozen times, both before and after Nintendo, but somehow they never seem to stick. Street Pass may have been the most successful iteration that I'm aware of. I think that it's hard to get critical mass. Users are excited at first when they set things up, but after a few days or weeks of not getting any hits, they tend to lose interest and turn the service off to save battery life.