Being homeless and panhandling almost go hand and hand. When I first became homeless, I thought that I would never panhandle, and me being young thought that I could survive on selling dope, shoplifting and the various other crimes I would do to support myself - well, after about a half dozen stays in the county jail (adding up to several years), I finally picked up a piece of cardboard and "flew a sign" as they call it around here.
The biggest issue right now is the police. You cannot stand on a median in Florida and fly a sign as it's illegal (according to the police, it's a safety issue). So, at first the police will give you a warning, then a citation, then jail. It actually takes you to be pretty ignorant to be taken to jail for it, as most of the police that I've encountered will barely stop me for flying a sign, and will only do it if I'm doing it somewhere where they really don't want you to (usually upscale places - gotta maintain that image!).
The other problem i encounter is the people that yell "Get a job." or something like that, that have never walked a day in my shoes and will never understand why I'm here holding this sign and just want to be assholes to make them feel better about themself.
Next time you see a homeless person holding a sign, just remember, we are all going through something, and we just need a little help and most of us are actually really kindhearted people.