I have always pre-washed fabric for the above reasons. A couple of days ago, I decided I wanted to take a break from a very complex quilt and do a simple, easy fast project that was waiting in the wings. I needed some solid black, just 1/8 yd, so I found a large piece in my stash and cut some off. I so badly wanted to just start in on it and not prewash, but because it was black I decided to wash for fear of it bleeding. I stuck it in my sink to soak for a few minutes, then went back to rinse it out. It kept bleeding and bleeding, so I kept rinsing, as I squeezed I noticed some pieces of fabric that were loose from the whole piece. When I opened it up, the fabric was riddled with holes and tears, it was disintegrating in my hands! I am so, so glad I didn't get it sewn together and then have that happen! I don't remember anything about where, or when I got that fabric. I only buy good quality fabric and have always, so maybe someone gave it to me. I took the whole large amount and tossed it in the garbage. I doubt if I will ever be able to skip the pre-wash step after this!