I think you can actually build a fairly competitive HU bot for 100bb games with very simple means (rules based with a bit of statistics thrown in, no opponent modelling or advanced features or learning). At 200bb it's a lot harder and researchers that approach it from an "understanding of the game" POV rather than a "pure computation" POV have a tougher time.
Edit: I only know Doug (aka WCGRider). Wish they would play against Ike Haxton, jungleman12, sauce123, Galfond or Durrr