I do remember something now from a trip to Germany. I was in the Augsberg Hauptbahnhof, getting ready to catch a train back into München. I had not yet bought my ticket, and was approaching the ticket machine to buy it. A teenager approached me, said that he had a weekend ticket, and if I paid him ten euros, I could ride with him as one of his friends (since up to five people could travel on one ticket).
I was kind of apprehensive, but half-heartedly agreed to go along with it. So we walk up to the platform and I get introduced to about 3 other teenagers. Then he asks me for the 10 euros. I told him I would pay him when we got on the train. Then he said he wasn't travelling on this train, but I was going to be riding with his 3 friends.
At this point, I backed out, said I'd get my own way, and left them. Was it a scam? Who knows. Maybe it would have worked out and I would have gotten a slightly cheaper ride, but who knows. I am very wary of scams like this and will gladly do anything I can to disrupt some low life's attempt to steal my money.