For me it isn't a question of being duped or scammed. It's a question of whether the gift is really going to help them. It turns out this is a very difficult question. When you give money to a beggar, you are saying "great job! here's a bonus to encourage you to keep begging!". At the same time, these are usually people who are in need. I also know that substance abuse is close to certain. I don't have a good answer. Most of the time I give nothing. Occasionally I'll hand a guy a 20, without regard for his story or whether I'm being scammed. It's a gift given freely.

What I know for sure is that I can be polite to them. Recognize them as humans, not treat them as lepers. If they engage me in conversation ask their name, where they are from. But usually ignore them on the ask. Because I can't rationalize that it would help.

But it's not an easy question.