@Lafu, it seems to me that you and @nakamura12 are not friends, collaborators on any project, or that you may belong to the same local board - so I wonder where this user got the idea to contact you and ask for $5? To me, such a move is strange to say the least - I mean in the sense that you're asking $5 from a complete stranger, right?
I think it's good that you opened this topic, because if nothing else, maybe some people will realize that they shouldn't ask for such things via PM.
That's exactly the angle I'm coming from. If I need $5 loan or whatever it's called, I will first reach out to my local guys in the forum and they'll gladly help off the forum. If I cannot get from my local board guys, I think I will ask a few of my close forum friends. I don't see myself asking a total stranger for a $5 loan. The amount is small but looks fishy.
I don't actually blame Lafu for making it public. Just imagine that a somewhat reputable user asks about 20 persons for a $5 loan and 15 persons reciprocates. So, Lafu just want to be sure he is also not asking several other users for $5.
It seems Nakamura12 perceived Lafu as a cool and rich dude who can easily split 5 bucks without thinking twice.