Hell, no! They must be slashed!!! Slash, I say!! I know! I look back on that statement that I made all those years ago, and laugh, and laugh, and laugh. I mean, I'll now slash characters simply because they were in the same room together! Hell if someone wrote a good fic for it, I would probably follow a ship in which the characters never *met*.
Once you get bit by the slash but, there's just no stopping :P