The true value of programs like this won't be as evident in the short term. I think we'll see alumni of these programs fostering communities and developing innovative ideas with each other for a long time to come. I moved to NYC after a hackNY internship and have no plans to leave any time soon. I see some of the people I interned with on a daily basis and almost all of them on a monthly basis.
hackNYer here. 4 days after hackNY is over, and I went back home to hang out with old folks, you realize how important and why living with other fellows is definitely the key, always doing something cool, learning, or teaching other people. That's why it's unbeatable.
The fact that it's in NYC where the startup scene is still far ahead from what its like in SF also adds to it, because you are sort of bound to hang out with other fellows as you are (likely) coming from other city, and since it is NOT SV/SF you don't know many (if any) people working in tech there.
Great article! I can testify to how great it is to go from knowing few people interested in hacking/startups to being surrounded by them. I'm not a hackNY fellow but I did just move from Philadelphia to SF to work at an awesome startup. I've learned a ton on the job (in just a few months) but the best part by far is meeting intelligent people with similar interests.