In 2016 there are 44 pending initiatives relating to Cannabis regulation alone.
Ballotpedia keeps track of pretty much all major initiatives-that could even be used to
automate the process of creating markets and judging them.
I think dealing with Cannabis US State Initiatives could popularize the site because of the passion these initiatives attract. I would ideally like to see predictit.org allow betting on any initiative that appears on ballotpedia.