2) I use the heuristic that where there are more participants and intermediaries, it is more likely that something ugly will happen even if the original intentions were noble, which is already a big if.

3) I prefer improving my own neighborhood which also affects me, to some abstract global goal which I find less tangible.

EDIT: 4) I am put off by the grandiosity of "saving lives" far away, and I prefer more modest goals, e.g. provide a warm soup for the local soccer team.