I've found it's just people in general these days. I was listing my 73 Ford 250 Camper Special for sale on ebay for $2500, willing to negotiate. I had one guy offer $1500 because he had to cover the costs of driving it back to MO as part of the purchase price. Another offered me $800. My brother has been screwed repeatedly by local people on various deals; one said the car had been in an accident but was all repaired - fast forward to pulling the carpet from the trunk to find a crushed spare tire well and bent strut tower...or the guy who gave him $250 down on a truck and never returned to pay him the rest.
Or larrysouders on here who saw me advertising my Dirtbound Extreme Winch bumper for $475 or my rear bumper for $200, shows up with $300 in his pocket for the front bumper. After claiming I listed it for $200 and being proven wrong when I pulled up the ad on my phone, he offered $300. When I said no, he left, then called back 5 minutes later to offer $300 up front with $75 via Paypal the following Friday. I felt bad for him, driving all the way out here (bout 2-3 hrs from his place), plus, it was his "birthday", so I agreed. He gave me the $300, I gave him the bumper, and I never heard from him again.
On the flip side, I've had mostly positive experiences through Craigslist...it's all about who you end up dealing with. Idiots and good guys all around.