The Straight Dope: Why does the shower curtain blow up and in instead of down and out?

I always thought it was convection; hot air rising out the top of the shower stall sucks the curtain in. But it turns out that cold showers do the same thing, thanks to the Coandă effect

You learn something new every day :-)

For much more, see Shower Curtain Effect.

(Update: The Straight Dope revisisted this discussion, concluding that the original article was false. )