[Preamble: I debated about which forum is the best to post this in. If members think it belongs in a different forum, let me know (PMs preferable to OT posts).]
Often here on prospers.org and on the old Prosper forums we have lots of debates about what one can or cannot do to collect a debt.
Here's a reputable guy's analysis in plain English of the things a debt collector can or cannot do