I don't try to guess whether they are scamming me or not.
I believe if you give, do it unconditionally without judgement and from the heart.
For that , you will be blessed.
If they are doing it for the wrong reasons, then they will be judged. Remember, we are all human beings with only one JUDGE !
Charity is both a gift and a curse. Remember if you give a man a fish , you feed him today. But if you teach him to fish, you feed him forever. Old words, wise words. But words do not feed people or their souls. Actions do.