The biggest issue I have with CL is clueless sellers.

One posted a picture of a built up bike with a top end Fuji frame in a front yard (a frame that was offered only as a top of the line frame/fork). After an hour of driving I asked him where the bike was. He pointed to the Sports 10 on the front porch. I said that the picture wasn't of the bike itself. Apparently, he decided just to post a picture of a brown Fuji that he pulled from the interweb instead of charging his camera. Knowing the guy was clueless, I explained his error and then he said that he was getting responses from around the midwest about it. Now I always ask if the picture is of the bike being sold (seems strange to have to ask, but...)

OTOH, it's just that type of "semi informed" seller that netted me some great deals too.