Unless you just arrived from Mars, odds are high that you have see the panhandlers working the off-ramps. It is a pretty simple scam. Look scruffy, carry a sign with a sob story, and make eye contact with the drivers waiting at the light. While there might be some seriously needy people, the vast majority of them are completely a scam.
Oh, yeah, some will have heartbreaking stories, but take note of how many of the pan handlers look pretty well nourished. Hmmmm.
Of course, "good" corners are popular, and that can lead to panhandler fights. Yesterday, on my way home, there were two groups of beggars arguing rather loudly, and threatening each other with knives.
I guess there is competition in all human endeavors.
(for the record, your donations are far better given to one of the organizations who help the homeless.)