'An open door for the talented would help Facebook's bottom line,' Collier concludes, 'but not the bottom billion.'
By this definition of "help", the only way that the US can help even a small portion of the "bottom billion" is by becoming part of them, which isn't in the world's interests and certainly isn't in ours. This video explains it very succinctly. At current immigration levels, the US population is slated to reach half a billion people by 2070, and top 625M by 2100.
Forget what this will do to our domestic standard of living -- consider what it will do to our ability to continue helping ANYONE in the developing world. With any luck, we will barely be able to maintain a poverty level here at home above that of today's banana republics.
What the hell is so wrong with having a meritocratic immigration system, i.e. an "open door for the talented"? It gives those people who are genuinely pushing the boundaries of opportunity in their native countries a chance to realize their potential, while also enabling them to contribute to developments that will almost certainly benefit those same native countries. Symbiotically, it gives the US an influx of talent that is somewhat less expensive, enabling those developments to take place more rapidly and thus driving commerce both here and abroad.
We can't take in the "bottom billion", and we won't do anyone any favors by killing ourselves trying. They have to, as the saying goes, bloom where they're planted. The best that we can do to help them is continue to contribute to the global economy, which we can do better with an increased talent pool that's achievable in part by being judicious about whom we take in.