> Which technologies are still out of reach to most people in terms of price or required technological know-how?
Entrepreneurs have fantastic building blocks available today. In the first world price isn't a problem, it's know-how. Benevolent hacking can deliver a kid from poverty to financial independence pretty quickly if he's clever enough and can truly solve people's problems. That's an inspiring idea. At some point, laziness becomes the real barrier.
> What is the optimal size for hackers to be able to effectively collaborate but not be bogged down by excessive control?
That's an interesting question. I suppose the answer would depend on the quality of the hackers, the problem they're working on and the parameters they're working within.