I learned something last year about how you can get scammed by buying tickets off of Craigslist. One way this happens (I am sure there are others) is that people will sell tickets twice. Read on and I'll explain.
If you have purchased MLB tickets from Stubhub, you know that the common method is to print your own ticket instantly when you buy them. From the seller's perspective, they enter the bar code of the ticket when they sell it, which is how Stubhub can guarantee that the ticket is valid. Once the ticket is sold and the buyer prints it, the hard tickets still in the hand of the seller are no longer valid. I had an experience where someone sold me a pair of these void tickets, which visually there is no difference from a valid ticket, and I found out when the ticket taker scanned the bar code. Luckily I called the guy I bought from, and he came down and gave me my money back. In his case it was apparently an honest mistake.
However, there are some take-aways from this when you go to buy tickets on Craigslist. Here is a little safety checklist:
1. Trust your gut. I think many times when you talk to somebody and see them, you can get a good feeling of how trustworthy they are.
2. Volunteer to meet at their house to pick up the tickets. Not everyone is comfortable with this, but if you know where they live they probably aren't running a scam
3. If you do meet in public, take a picture or jot down their license plate number. If the tickets end up not being valid, then you have something you can look up to find them and report it to the police.
Personally, I buy and sell on Craigslist and find that following rule #1 works out the vast majority of the time.