I have a lovely few ounces of green merino/soysilk/angelina roving I was saving for a special project, and began spinning it this week. I usually spin with a light-colored cotton towel in my lap for better visibility. The towel wound up in the laundry, and somehow there was still some roving rolled up in it. Well, you know the rest.
It's what I've always told my students: wool in the presence of water, detergent, heat and agitation = felt.