See, now that's why I don't pre-wash ;) !
I do run a damp white cloth over, esp. dark colors & batiks, but I've never had a problem. The only thing that bled at all was a Debbie Mumm Christmas print. That darned thing was still turning water pink after three washes!
Edited to add that I do pre-wash when needed for swaps, and you are right - it can make quite a mess, not to mention the knotted up wad the fabric itself becomes.