What is the check on the managers? Why can't they just issue themselves credits?
Listia credits are centrally controlled, the people who control it can do whatever they want, including give themselves credits. This is like any other credit/money scheme with central control (and unlike bitcoin). In fact, you can get credits at random times for doing things like checking in, listing auctions, giving feedback, etc. Thus, there is inflation on Listia.
Craigslist freeloaders are the people who actually buy stuff, is this right?
As I mentioned in my second post, the freeloaders comment applies strictly to the "give away free" section of craigslist, so no, they don't actually buy stuff.