What we do know though, is what our stance says about us. In this situation of uncertainty, what you actually have is a choice between two risks.
1) You risk depriving someone in need.
2) You risk enabling someone's destructive behavior.
The big question is, why are you willing to choose one over the other? I personally believe that, especially in situations where you cannot be sure you're enabling someone, risking depriving someone is the greater of the two evils.
I've gotten into this discussion with a lot of Christians, and I know it's a common source of conflict. I ran into a new version in the post of a fellow jiujitsuka asking for donations to UNICEF for the crises in eastern Africa. If you'll take a look, one of the first comments is, in a nutshell, "Their government is the problem. We need to solve that problem first."
I agree that social institutions are frequently the problem. (I also believe that the either/or fallacy is a complete cop-out). Amartya Sen has produced some compelling essays on the the concept of famine. One of the recurrent themes is that famine is not an issue of supply, but instead, access to supplies. While I do believe it is imperative that we not ignore the big picture, lets be honest--most of us have very little chance of influencing foreign governments...and honestly, God calls us to do what he's enabled us, which in 99% of cases, means doing small things to make a difference in people's immediate, short-term lives.