People who are either unrecovered enablers or addicts of some description themselves will sometimes try to crash our boundaries; a friend of mine posted a warning on FB about a local heroin addict who will come out with a sob story about how she needs to get to her mother's in a nearby town because ... (insert fabrication of your choice here) and can you give her the money for the taxi there. Predictably, when people have offered a lift instead, she's lost interest...
Others responded that giving money to addicts will do them no good, if you want to help the homeless - donate to the organisations which help them etc etc - until a very angry person intervened saying that nobody had shown any compassion to this poor addict - who really needed money when she was in a state like that, and that we were ignorant bigots, middle-class apologists and racists (despite the fact that race had not featured in the discussion at all).
I stopped following the discussion at that point...