I hate saying this because it happened to recently but here goes.
I was moving out for the first time and i found a sublet. The guy was there with his girlfriend and seemed nice enough, we agreed on a rent and a deposit and I requested his lease ( to see if he was authorized to sublet his place) and my lease. Everything looked in order and the lease terms were agreed upon. I signed it off, got my copy, put in a deposit and he left. Not even a DAY into living there, someone shows up and lol & behold its the 'real' owner, who is pissed that someone is renting out his place without his knowledge. The person who i signed the lease to and gave the money to was a former tenant who couldn't afford rent, but wanted his money back, so cheated me off to get his deposit. Later on, i checked my state's judiciary system and learned that the person wasn't even born in the US and he had several court cases against him, ranging from child support suits to car payment collections. I never heard from him again, and of course i never got back my deposit. Luckily I had been saving for a few months and was able to move in to another place for cheaper.
Losing that deposit sucked, but in the way it life-changing in a good way. My new roommates are awesome and well connected so i've benefited from their contacts and i'm alot more conscious about where my money is going.