Um, on the SF/Sci-Fi thing... have you seen Harlan Ellison's take on that one? It's included in an essay he did on the Heaven's Gate cult some years ago. I tend to agree with him on this one:
Harlan Ellison Webderland: Harlan Ellison on Heaven's Gate
And I'll be honest: I don't think there is such a thing as an interchangeable label; each phrase or word (and this applies to all such, not just to this particular instance) carries with it a host of connotations and layers of meaning. Generally speaking, it's that inability to distinguish between them that I feel is a part of the entire lack of critical thinking/discrimination (in the positive sense) that has so muddied the clarity of discourse over the past several decades, allowing for muddled, half-baked thinking to pass as profound insight....
(Steve: Just for clarity, this isn't aimed at you. It's a general observation of how imprecise our thinking -- and therefore our ability to communicate well -- has become....)