It doesn't? I was pretty sure that you could message people now via MiiVerse - maybe it's only reserved to friends only. As far as the whole avatar/anonymity thing, nothing's stopping you from sending the forementioned friend request saying that you're a gamer from the neighbourhood, you two just Street Passed and if he/she fancies a game of
*insert title*, you're open to have some fun together. Online is a powerful thing, y'know - once you know the person better, you can meet in real life if you please. I do see your point, I'm just not that kind of a shopper. Approaching me in a store because I seem to have similar interests would result in creeping me out -
"thanks, that's very nice of you Mr.Total Stranger, I'll be on my way out now".