I haven't done any transactions on FABO, but I'm always really cautious about internet transactions. One of the things I like to do is check and see if the person has an ebay account, if they do, I check their feedback. I do a quick google search for their handle to see if anything funny comes up, I try to pay with a method that if it goes south I have some sort of recourse, never deal with high dollar stuff without seeing in person, and lastly I use the old adage...if it's too good to be true.
Obviously there are a few members here I would do business with without going through that, but they've been around a long time and have done so much without any problem. Others that I don't recognize or are new to a site within a month or with only a couple of posts, out of country etc I stay clear. Doesn't matter if they're looking to buy or sell.
Guess I'm just paranoid, but I've never been scammed online, so I hope some of those things help people.