CD, you seem to think I'm targeting specific things with those questions, and perhaps I am...like the Antiballistic Missile Treaty, for example.
Badge, the idea of donations is one that is widely shared. However the ability raise donations generally pales in comparison to the ability to tax. That's not universal, but there's a reason that governments rely on taxes and not donations. My favorite example, because I've lived it, was seeing local school advocates bust their buts to raise an astounding $2M to support our schools. Then we passed a tiny property tax increase--an amount far smaller per person than the average school donor was giving--that instantly raised five times that.
There's another problem with the donation model: donors only give to things they like, as in personally like. Who's to say that the donors have any expertise in what works? Example: I admire that Bill Gates wants to donate huge portions of his wealth, but does being a wealthy tech maven give him the expertise to determine what is best to address a particular social ill. What if he's only willing to give his money to a program that the experts and community it is intended to help think is a bad idea? Whether it's the Koch Brothers or George Soros, being wealthy doesn't make someone right.
That's not to say that I oppose local foundations and philanthropic funding, but it tends to be a good supplement, not the main driver of policy.