Yeah, a quick read of the relevant regs tells me Fanduel is gonna lose this one (Unless i've missed something)[1,2] The law on this is pretty clear, and they can't unilaterally decide not to apply the gaming regulations of the state, or change them through their contracts. (They can decide not to do business in states they don't like the regulations of course) BTW, somewhat hilariously, the part they "..."'d is just…
But these are still contracts, subject to the basics of contract law. Contracts are not meant to be gotcha moments where one side leverages the mistakes of another. Look to the booking of flights. A small error here and there on price will be enforced. But a monumental error leveraged by people who would otherwise not fly will nullify the contract (ie hundreds of people suddenly booking first class travel London-Joha…
Conversely, bookies do not have to take into account whether pundits are likely making a mistake. Betting schemes thrive on the appearance that the bookie made a mistake. Either way, the places I know limit possible wins (e.g. 1000$ for a bigger, casual one). And even if not, they should be allow to take bets only if they can back it up.
That a pundit could not nullify the bet for the same reason is an edge the bank system abuses to no end. It's institutional. Since they don't have rigid rules for liability in computer security (e.g. in IOT and all the data ex-filtration cases) or code correctness only means the court would resort to opinionated decision on a case by case basis and precedent would only mean they can, not that they should, if the situation isn't exactly the same. There is bound to be precedent for exactly this case, which would open an avenue for abuse by the bookies. I don't think it's clear at all.