This is a sad but true aspect of the holiday season, but it's always good to remember that some folks out there are genuinely in need, and that not everyone asking for a little help is a scam artist. This is a subject that can/will cause some heated debate, but in my opinion it's always best not to judge everyone by the same rule, especially if you've never been in that situation. Speaking generally, and to no one person in particular, I believe that If you've lived your whole life with a roof over your head, folks who care about you, a good source of income and never had to worry about where you're getting your next meal, surely you can afford to kick down a few bucks to someone who hasn't. Again, this is a general observation, as I can't possibly know what any one person has been through.
I've personally been in situations in my life where I had nothing at all, and may not have survived without the kind help of strangers. I always did my best to find work wherever I went, so this hardly ever had anything to do with money, but came in the form of food, water, shelter, stopping on the highway to pick me up stranded in the middle of nowhere. Being out on my own as a kid I learned a lot about the indifference of a great number of people, but I also learned that there are still good folks out there, and I try to pay it forward every time I see someone in need. It doesn't have to be giving money; if i'm unsure about someone I'll ask if he/she would like something to eat. If they refuse the food, they're probably dishonest. Personally, I don't really mind if someone is honest and tells me they want a few bucks for a beer. It sucks being homeless, with nothing and no one, especially around the holidays when it's cold outside. If you're honest and tell me you just want beer, hell, I'll buy you a beer.
Again, it's impossible to deny that there are a great many scammers out there, I just wanted to put it out there that this is not always the case with everyone.