"I think most of our bettors have bet in Las Vegas, where they buy a ticket and once they buy the ticket, it's a bet. If the book made a big mistake, oh well, they are obligated for that ticket."
Please stop making your arguments based on that incorrect statement. Mistakes happen everywhere, and I can assure you that books in Las Vegas can and will cancel a bet on a "bad" line, at their discretion. They simply go to the computer and "freeze" the ticket, so that the cashier is unable to pay it. They don't track you down or email you, either. They just cancel it.
The difference between Las Vegas books and offshores, though, is that Las Vegas books tend to give the customer the break if the line is not terribly out of line or the wager is not too significant. They know the customers may be spending money in other parts of the casino, and it is not worth it to piss off customers,spouses, their friends, etc.
And with fewer lines to post, and customers sitting in the book that can see a mistake on their screen (and who will actually tell them about the mistake), as well as supervisors who seem to be more careful, you don't get as many bad lines in Las Vegas. But they will cancel them, if they want to.