Well, I'm gonna weigh in here, but with a somewhat different opinion.
Like most of the opinions you've already received, I ALWAYS pre-wash; the purpose (for me) is to 1) remove any excess dyes in the fabrics; 2) pre-shrink the materials to eliminate any excessive "puckering" once the quilt is put together; 3) soften the "hand" of the fabrics. I hate working with fabric that feels like paper (which is why I NEVER use spray starch).
However, I do not use detergent. Instead, I first trim the corners off the cut edges of the fabric to help alleviate fraying (although this doesn't always eliminate it). It also makes it very easy to spot a pre-washed fabric in my stash: if the corners are clipped off, it's been washed. I then put like-colored fabrics in the washer, adding in a fistful of kosher salt and about a cup or so of white vinegar. Use cold water. Once the washer is filled, allow it to agitate for a few minutes, then stop the washer to soak the material for as much as 20 minutes or so. Then drain the washer and allow the rinse cycle to work.
Remove and dry until just damp-dry, then press as soon as the fabric comes out of the dryer. This will help to complete the drying process, your fabric will be wrinkle-free, and you can fold it flat for storage much easier.
Why the vinegar and kosher salt? The salt is slightly abrasive, and between that and the vinegar, it helps to "set" the colors in your fabric. Vinegar also cuts through any grease or oil-based finish on your fabrics in the event there may be some residue left over from the processing plant that created your fabric.
I know it sounds a little "hinky" to you newer quilters, but I've been quilting for nearly 40 years and this is the way I've always done it. Naturally, this goes for 100% cottons (not velvets, satins, or laces that you may be putting into a Victorian crazy-style quilt, for obvious reasons).
Okay, everyone, now that I've advised you of what we did "back in the day", I'm climbing off my soapbox. History class is through. Who wants to chime in next?