@all: Gamblers, have a different mindset than those who are engaged in commerce. Let's just call it entertainment, and not get too preachy. Gamblers will pay substantial fees for entertainment that those engaged in ordinary commerce will not (or cannot) pay. (15%-20%, typically, at a parimutuel US horse race; 40-50% at a typical US State lottery; 5% at American roulette; etc.) I don't think it is possible to raise the fees in a way that would make SD unprofitable, without raising the fees in a way that makes bitcoin unprofitable for many other economic purposes.
The only reason gamblers would pay that sort of fees is because it's an extremely regulated business and as a result it's very uncompetitive.
SD would have to compete with other gambling systems off the blockchain and it would soon become a rip-off in comparison.
On top of that, all the current abuse would become so expensive they would be squint rather soon.
And on top of that, it really isn't a business that can grow so big that it will phagocyte any possible blockchain, provided there are some sanity limits (namely fees).
If you think gambling can grow so big, even at fees as high as 5%, that it will make any other business uncompetitive by land-grabbing blockchains of any transactional performance, then that would basically prove the whole idea of Bitcoin inviable. We would have to abolish complete anonymity in transactions and start monitoring what people do to stop gambling.
I'm willing to bet (

) this is not necessary and that gambling would stay within control just by virtue of fee-based self-regulation.
Gamblers don't choose where to play, because of the fees (or rake, or house edge, etc)... they choose to play because of the games being offered... the rake is secondary.
If fees were the primary choice to choose where to gamble? Everyone would be playing at Seals With Clubs. (referral link in my sig below