I've got to echo the comment by lowrider about those that have mental health issues - there are some people who aren't there by choice and get stuck in a cycle, or don't know any better because they don't have the mental capacity. You need to distance this from tramps and crackheads really.
I won't give to alcosmelling tramps or those clearly abusing drugs, because it's kinder not to fuel their habit at the end of the day. I will happily give to entertaining buskers and those homeless I make a snap judgment on as being worthwhile.
A homeless guy in brighton recently didn't ask me for anything but I walked past with the g/f and half a pizza we'd literally just come of out Pizza Hut with, I walked back and said 'hope you don't think i'm odd, but would you like some pizza?' he was genuinely overwhelmed and really polite, and when i walked back past ten minutes later, there he was, tucking into it.
Having come into contact with homeless people with mental health issues through volunteering and working with young people who become homeless, I can tell a lot of you now that you are very wrong about your uneducated thoughts about a decent percentage of these people.
And try getting benefits without an address...