there are several site advertising provider serves. I'm curious what you think the differnce is between them? It seems that Craigslist is the leading culprit in scams, ripoffs, muggings (as we saw this last week), etc. Is it just Craigslist? Do the others have more stringent posting requirements or verification  process the providers must go through? I don't remember seeing Backpage or Phx 411 in the news (early dimentia,).

Let me add that I wholly endorse doing your homework & that there is some inherent risk with the hobby.  But still I wonder why Craigslist is the one with the trouble?