+1000, Now You're lernin'
There's no such thing as it's mine until it's mine. (Yogi-ism)
I've been very lucky with CL both selling and buying. Folks don't believe me, but when I sell I've got a Nut-Case-Filter. I insist they leave their phone number in their e-mail via CL and never list my number. It's amazing how many people that low ball or string you along, don't want you to have their phone number. Straight up types who deal above board aren't afraid to leave their number. When selling, this simple rule has saved my lots of headaches.

When buying, if it's a really good deal, I know I can only get the bike if I offer more than asking, and I've done that. Sometimes it works, sometimes not. Overall, my luck is good, I've only had one idiot who sold a bike to someone else after promising it to me.