Actually, I think something like this would work...
The odds would be determined by how many ppl bet on whatever outcome side. The money is kept in the chain as long as the contest runs and the the grader of the contest would receive a small percentage of the pool.
Been working as a software developer for sportsbetting/horseracing/casino operators for the last 15 years in Antigua and i am sure that even pro operators would be interested in something like that.
Yeah I think the market for this is big but it's a huge project that I feel requires a few other DAC's to appear to create services that could be utilised to make this happen. My weekend is looking free so I'll try and knock up a break down of how this may work (please anyone else feel free to contribute a 'vision', that's the point of DAC's in my opinion, we all contribute).
I also think it'll take a while to implement because it's an example of a DAC that would have to interact will physical entities (i.e. the athletes, teams etc.) which most of the other ideas proposed so far don't extend into (short I suppose of the end users/developers/moderators). In my head I can see a future world where there would be DAC's that act in a similar fashion, take for example of power plant DAC. It would require physical generators to produce the energy so there would be an overlap with the digital corporation and the physical products of the real world. These sort of projects, at least to get to the scale I imagine them, would require very large amounts of capital which means more promoting the idea of DAC's to the general public to get investors/developers/whatever interested (I still encounter friends who don't know what bitcoin is despite it being in the News heavily at the moment...).