You're right Daniel, a person can be scammed in many ways - especially within the realm of charitable endeavours.
God requires us to be good stewards of the resources He provides (such as time & money), yet also asks us to give in faith that He will do more with the portion we return to Him - such as tithes - than we can do with all that He allows us to use.
I think it's important to exercise due diligence with how & where we help others, but once the decision is made and the action taken - rely on God to do what's best with your gift... because it's out of our control at that point anyway.
Isn't that best for all things?
I say "Do your best and trust in God to handle the rest".
p.s. He really enjoys it when we do that!