I should also add from the books point of view
They are in a bind - not with this issue, but with booking horse racing.
I have to believe books that have built their reputation on fairness - the WSEX, Cris, Pinnys, Hollywood, etc of the world - the top notch most fair books really do not want to offer unfair bets. I do not believe they want to offer bets that pay 100/1 when they should pay 5000/1.
On the other hand, they do not want to have exposure that could topple them. I would feel very insecure playing at a book that has no cap on superfectas or whatever. What if someone hit a $100 superfecta for $100,000,000 or whatever and put Pinnacle under... These books are not in the business of offering lotteries without the security of a pool.
More than likely these books really don't want to book any of these exotics. They are in a no win situation - book it fairly and chance huge exposure. Book it unfairly and look sketchy.
The problem is the client demands they book the action. More than likely 90+% of the people who bet a trifecta yesterday have no idea what the real odds should pay. They bet football all year, have a few bucks at Pinny or WSEX and are happy to lay down $2 to win $600 and are happy to win $600 when they win. If these books did not offer horse racing, these customers would be upset and go to a book that does.
Thus, each book must offer horse racing even if they don't really want to offer unfair bets.
You can't fault the books for doing this.
But that being said, I think their limits should be very clear -especially on the derby. YOu can assume anyone betting the tampa roundtrack horse race will know to look at rules, but most betting $2 on the derby will not. Every book knows this and if someone goes to bet a trifecta or superfecta or any bet that could go over the books limit for risk, on the confirmation page in huge bold letters, it should say "Regardless of what is paid at the track, our limits on trifectas (Or whatever) are 300-1 or 1200-1 or whatever. We keep these limits to provide a secure wagering environment."
Then no one ever has a complaint.
Another option for the books is to buy insurance. I doubt these books want to take the time to lay off all their exotics, but they could buy insurance. For instance, when Taco Bell offers a free taco to the whole world if a meteor hits a target in the ocean, they buy insurance from a company like Lloyds of Londonm, etc. They probably pay Lloyds a hundred grand and are covered for the $50M in tacos if the target is hit. Lloyds is in the business of taking risk like this by selling 1000s of low likelyhood policies. A book like WSEX could buy a policy from Lloyds for a reasonable price that would pay off all horse wagers that win over $100K or $1M or whatever they want. They could then be the industry leader with actual payout odds and be secure doing it.
-Sean