I make my quilts as "utility" quilts, meaning I expect them to be used and loved and washed. Since I have no control over what others do, they have to be able to withstand regular detergent.
Depending on the intensity of color saturation and contrast, I may decide to prewash. Most often, I end up not prewashing and tossing 4-5 color catchers in the laundry with the finished quilt. So far, so good.