You also get entered into a drawing for $50 Amazon gift certificates based on activity (not based on performance - they're don't want to touch gambling regulations). I have gotten 2 this twice now with pretty low activity, which is nice.

The current and previous questions were focused on geo-political predictions which proved to be a surprisingly interesting to someone who doesn't really follow the news to closely. It provides a nice alternative way of learning about the world other than headlines - each question is a mini research project to quickly learn about the developments of North Korea's multistage rocket program or the likelihood of US increasing certain sanctions.