I've had the worst luck with trades, which is why I only do it now with people at reputable boards where there's actually some accountability-- places such as this, for example.
Had one trade a few years back that took me about four months to complete, including me threatening to file a mail fraud complaint on the kid...
I was trading him four signed cards of mine for two of his. In early August, just after I sent my two, he told me he could 50/50 the Marlins and Giants, so I sent him a bunch of stuff for them. A month later, I still don't have my cards from the original trade. He says he was busy and would get them out in the following week. I asked him about the 50/50 and he said he gave the cards to his cousin to get done and now his cousin wouldn't give them back.
So at that point, I was out about 70 cards and four signed ones. In mid September, I asked again where my cards were, and he said he sent them "a long time ago." Two weeks later I ask him again and he says he sent them "a week ago." So I called him out on it and said if he didn't get my cards to me within two weeks, I'd file a mail fraud complaint with the USPS.
A month passes-- we're at the end of October now. Nothing. I ask him where my cards are. He says-- third different response to that question-- that he would be sending them out in the following week. I tell him I'm filing a mail fraud complaint as we speak. I wasn't, but I figured I'd see what would happen.
He called my bluff and a week later I had the two signed cards waiting in the mailbox with a note trying to apologize profusely. I later learned he had ripped off several other people on 50/50 deals and trades. So if a Josh Bloom from Boca Raton, FL tries to trade with you, RUN-- DO NOT WALK-- in the opposite direction.
Never got my 50/50 stuff back, but whatever.