After reading the thread about the 125 lb all-star match on themat.com, and the controversy about the takedown call, I propose the following rule:
If you are being held on your back, you are taken down. Doesn't matter if you are hanging onto an arm or a leg or whatever.

Maybe (almost certainly) I don't really understand the intricacies of folkstyle wrestling, but it drives me crazy when someone is laying on their back not giving up points. It just seems wrong.