They used to be very active in the NYC Meetup scene, too. ~~I think I visited at least two of their offices and the second was was stunning. It was far south enough and high enough that there was a nearly unobstructed 200° view of the southern end of Manhattan, both rivers, etc. It was also beautifully designed and had an obligatorily huge, open, stocked kitchen.~~ (This was actually Two Sigma.) They were also using exotic tech back then, too, like OCaml, which is itself a form of marketing and helps with recruitment.

Moral qualms aside, it must be a fascinating place to work.