I got more hits from one evening of walking down the Las Vegas strip with my 3DS on than the entire weekend I spent at Disneyland. Very strange.
I don't think its all that strange. You rarely see people bring games to Disneyland, and those that do are usually kids who don't have the street pass set up. Even seeing kids with it is rare since its so easy to have things get ruined or lost. With Vegas though you can get people driving through the strip who are heading to their hotel to check in, etc.
I remember when I was at E3 last year and my 3DS was blowing up with new miis showing up. It was cool at first, but upon realizing that I have a 10 mii limit before I can have more come in, I just gave up and ignored it. I didn't get very many people at comic con. I usually get a lot at Anime Expo though, which really isn't surprising.
It gets even worse when you have a bunch of people showing up in your streetpass enabled games. If youre really committed you just end up finding somewhere to sit for a half hour collecting all your stuff. I wish nintendo would increase the limit. Considering streetpass was made with mostly japan in mind, it seems silly to max out at 10.