Editor's note: Living Cities' CEO, Ben Hecht, writes about Black Rock Impact, a social investing platform from mutual fund giant, Black Rock Funds. It makes me nervous and hopeful at the same time. Nervous because I've never been a "bottom of the pyramid" kind of guy. That's the theory that good money can be made off the world's poor. But the points Hecht specifically makes about urban USA areas taking advantage of these new funds to build micro-lending and such things makes me hopeful. Enjoy.