What the absolute fuck? I'd have left and called the cops. There had to have been some kind of warning sign though?
I've had 2 experiences on craigslist, the first was enjoyable, with the dude being exactly like the pictures he sent. Albeit, we were both virtually virgins at the buttsecks, so it wasn't /great/, but it was enjoyable.
The second time around was an older, bear type. After rigorous emails for information, we met at his house. He was very nice, but his pics were obviously older, as he was a bit older, and larger than he had appeared. I told him to put on a condom though, and he said he did, but when it went in, I knew he didn't. When I didn't respond to his movements, he withdrew and I said I was emotionally unstable and needed to leave. He gave me a hug and I left quickly. Sorry, I don't fuck around with barebacking. Sweet old dude though, he was a good sport about it.
I usually get pics, stats, and make sure they give me a valid face picture. It's usually good to ask for a timestamp, to know the picture is real, written on their hand.
If you live in an area that's outside the city or spacious, and thus can't meet up before hand, it's always good to just chat the person up as much as possible to assess their person as much as possible.