MikeB and fistful covered it. It's not just hipsters, in fact they may be a smaller segment. Lots of environmentalists and other Birkenstock wearers are really into it (in CA, anyway). People you wouldn't otherwise expect, and not just for eggs, but meat too (though chicken is a vegetable). A person at the old job who was always totally raving about guns and hunting, was pretty proud to tell me she had started raising chickens and rabbits in her backyard, and how hard it was to kill them, but that she wanted to know where her food comes from. Apparently Mark Zuckerberg does the same thing.
A bit hypocritical regarding the anti-hunting, but I think overall it's a positive thing for people to see exactly what it takes to keep them alive. Baby steps I guess.