This has not happened to me, but I am a pre-washer of everything. If the colour is dark and coming off on surfaces I would think the dye is maybe not stable and could run. I know there are products to stop this problem (colour catchers etc. but I'm not in the USA so someone will help you there). So I suggest that before you wash it invest in some and you won't have a disaster on your hands.
Interestingly, I recently read my new OBW book, and it stipulated no pre-washing, so when I get round to doing it I guess I'll break my "rule", but only for that project. I just don't like nasty surprises.