Here and there, once in awhile, hostellers get scammed, robbed, or otherwise victimized. Fortunately, all three are relatively easy to prevent or recover from. Even more fortunately, hostellers truly are a better breed, and such occurrences are rare. There are people all over the planet who make at least part of their living by fooling people into parting with things of value. The example I described above is a big example in the budget travel realm.
Most stories are smaller.
Often, someone just befriends you for an hour or two, maybe at the bar or in the common room, then asks for a favor. Blah, blah, blah. Oh, forget it. No, that's okay. The bank is only 4 blocks from here.