Human computation! Not to be too #hailcorporate, but my job's pretty fun. It's using machine learning and humans together to solve problems. The fields pretty focused on labelling tasks, but there's much more to it. Having a large human workforce backed by a bunch of engineers and data scientists is like a fast-forward button on machine learning. You use humans and computers together to do things we really can't automate yet (or even ever, without general AI). ML meets cog-sci meets HCI meets crowdsourcing.
I understand the excitement :) - working on ML+human workers product too, but in customer support space. It is always fun to talk to people working on similar problems, especially in different markets. Would you like to chat? Please reply to my email (eugene.mandel at gmail) - I am in SF 2-3 times a week.