It's up to the individual.
Personally, anything faster than 1/15 is fine for me.
If I really don't want to have to worry about keep the camera still though, I'd prefer something like 1/50 or faster.
If I don't mind a bit of a blurry shot, then I can (and do) take photos at 1/4, 1/2 and 1. But you need some kind of support or extremely steady hands.