I ride the subway often so I see people who ask for spare change. I only give them money if I feel like it and depending if they look like they really need it. I use to feel bad when I didn't give anything but after sometime I noticed it's usually the same ol'beggars. Like one lady brings holds a card box sign asking for money while holding a child in her arms and pregnant. Most people I see dont give her money, I doubt she's in such a desperate state to be like that from the looks of her. My guess is that it's just a way to get people to give her money.
Oddly enough, there was one guy who asked for 40 cents at the stop I take the subway at. I did give him spare change the first time. A few days later I see him at the stop I get off at and he's asking for the same amount: 40 cents. I saw him do that another day. Another time I was feeling generous enough to give a guy some change. It wasn't a lot and he complains to me as I walk away. I'm just thinking to myself: I was nice enough to stop and give you spare change and you're complaining to me??