I asked them that. Here was the answer:
"Thanks very much for your note, and I'll be happy to discuss this with you. Spoonflower prints all fabrics with pigment inks which do indeed appreciate gentler handling than fabrics that you might buy at a retail store which have mostly been printed using different equipment and different dyes. In general, we recommend that you wash most of our fabrics (including the quilting-weight cotton) in cold or warm water using phosphate-free detergent for optimum results. After first washing your Spoonflower prints you may see slight fading, especially if there are lots of dark or saturated colors used in the design. This fading should never be dramatic, however. On a personal note, I have used Spoonflower fabrics in my own sewing projects (quilts, pillow cases, and a few clothing items for my daughters), and this has also been my experience."