Can you provide sources for this? Also, what do you mean "efficient"? If you mean there's no overhead, sure, so long as you don't spend any time trying to determine where the need is and just hand cash to the homeless guy you see on the street, but I care about effectiveness, and that's very likely not going to be "give money to the guy on the street near my office".

GveDirectly is better than most charities (which is mostly just giving money to poor people, but is a charity that does it intelligently). Additionally, the Against Malaria Foundation probably has a higher effectiveness.

The problem with depending 100% on people giving to charity is not that it's worse than depending on them giving money to the poor. It's that it completely ignores the various externalities that can be corrected through taxes and government spending. Would the world be better off if we cut government spending in half and send that money to AMF, GiveDirectly, and similar programs? Sure. But would the world be better off if we just cut government spending and hoped rich people would become more altruistic? Probably not.