I know there is at least one person interested in sports analytics for financial gain here ;)
The only issue is that you can't scale well but this only becomes an issue when you need to put down tens of million a week (i.e. when you have $50m+).
The barriers to entry are also getting higher as competition is increasing in the space (although limits are probably going up too). One big issue right now is data. If you bet on soccer (the sport with the highest limits), you need to spend at least $100-200k/year (before hiring programmers) on data to become competitive.
then after 2 years you would have billions of dollars. yeah right
The issue, as I said initially, is that you aren't scalable past $100m or so (without connections to the Asian books, which some people above have...apparently, some of the guys are able to put down multiple millions on most European soccer leagues...which isn't available to most). But yes, most of the funds run by the above people have been making 100%+ for years.
A lot of the market is not tradable though. On one end of the market, gambling is often a state monopoly with high spread and high margins (if not prohibited entirely), while on the other end there are large trades going on in private or closed circles.
(I cant recall the name of the company that makes these super highend net cards, which hedgefunds prefer)
LOL.
In sports, you can study your opponent to predict what they might do. In business, you can really only study what your opponent did during the actual game so to speak. For example, Microsoft can't wait for Sony to release the PS4 in order to develop a game plan for the Xbox. Both have to put forward their best effort regardless of what the competition may or may not do. In sport, you are training to beat 1 opponent, in business you are trying to appeal to the whims of the multifaceted consumer which aren't nearly as concrete.