From an uncredited forward to the amb list:

I  them.  On the playa.  Car camping.  Road trips.  They're
amazingly useful things for removing the body paint, quick sponge baths,
cleaning the playafied toes before someone massages moisturizer into them,
etc.

I have suspected that they were plastic based and shouldn't be burned, but
never had my suspicions confirmed. Until today when I called
Kimberly-Clark's consumer line.  (*note* this does not necessarily speak
for other brands)  Their Huggies brand baby wipes are made of wood fiber
on a polypropylene base.  Which means they don't completely decompose and
I'll be switching to their Cottonelle line of 'intimate' cleaning cloths.
Fully wood fiber based.  yay!