Thanks. Our complete stack is quite complicated, but a quick run down of what we're using: mysql, memcached, mongodb, gearman, nodejs, redis and puppet. (Node and redis are not in production currently.) The main language we use is php. I know, ugh, from all of you ruby and python guys, but good clean php is as good as any of the other language.

Yes, we have plans to expand the user demographic. Our product roadmap should help with this. We're just too constrained right now with engineering resources.