The tech behind whatsapp was pretty cool IIRC .. that's how I got interested in Erlang/Beam. These people were not your average CS grad or even your average googler.
http://www.erlang-factory.com/upload/presentations/558/efsf2...
Also, I got interested in Elixir/Phoenix after I learned about what WhatsApp accomplished.
I'm a bit surprised people are downvoting a technical point on HN but whatever.