I don't bet, nor use Steem Sports but I did see an increase in frequency of these posts and I wasn't aware it took such a large part of the rewards pool.

My suggestion for @dantheman is to have a "root" type of operation at the blockchain level, that can be subclassed in the client.

"content" and "activity-on-content" could be the root classes and they could be subclassed in a custom implementation.

Steemit.com could implement "content" => "article" (or photo, video, etc), "activity-on-content" => "vote". And SteemitSports.com could implement "content" => "event", "activity-on-content" => "bet".

There really are only those two main operations at the blockchain level and putting specific cases at the blockchain level would clog it eventually.

Also, having the custom implementation in a client could also help with regulatory problems (I'm not a lawyer, though). A gambling website is regulated independently of the WWW protocol.

Also, I have a few use cases on the gaming niche as well that could greatly benefit from such an implementation.