One thing to protect against in any kind of washer when felting/fulling sweaters is the shedding of fibers. Even a small sweater can shed enough to really gum up your pipes and/or hoses, so it's best to pop that sweater into a pillowcase that is pinned shut or a pillow cover with a zipper.

Here is some really great info on the subject of felting/fulling.
http://www.lusciousgracious.com/felt.htm

Ghostrider, that about sums it up!! :-)