Combine this with bandwagoners that plague every sport, and you have a lot of Laker fans on the East Coast, Heat fans in every city, etc.
I have a friend from Cincinnati who's a huge Bengals fan- he jokes that at least he's not a wizards fan. There is something there- fans of bad basketball teams have less reason to hope than in any other sport. Football has teams turn around almost yearly and baseball and hockey have minor leagues. With basketball, if your team sucks, there isn't much reason to think that it will be different any time soon