Just as all true Scotsmen [http://en.wikipedia.org/wiki/No_true_Scotsman] love haggis, all true fans [http://en.wikipedia.org/wiki/Fan_(person)#Etymology] have blades for moving air.
But seriously... as terms go, this one is subjective enough to boil down to "if you claim to be a fan, you're a fan".
Nothing like those newfangled suction-powered air-movers. No true fans, those!
Behold the Devil!
But seriously... as terms go, this one is subjective enough to boil down to "if you claim to be a fan, you're a fan".