Every bit increases the known magnitude of incompetence though. God knows how incompetent they really are, at least they managed to stay in business if that means anything.
This is what I think happened. The new FinCEN rules came out. It meant if you exchange virtual currency, you better be registered as a MSB with FinCEN. MtGox didn't want to do that, so they were working a deal to offload all their US accounts to CoinLab. Thus solving the problem. Turns out they back out of the deal, keep using Dwolla to handle US accounts, and end up getting caught. I have no doubt Coinlab dropped a friendly "tip" to DHS about MtGox. This is probably why they only went after their Dwolla, they failed to register as a MSB. Typical Gox failure, instead of properly try to solve the problem, they tried to work a deal, backed out, it blew up in their face. In terms of the Bitcoin market it's fairly minor. It's a boost to other exchanges, people will get registered, people will be legit, it's good for everyone overall.
This has wider percussions than satoshidice though if they are affected so is the entirety of Bitcoin gambling sites operating on clearnet.
You shouldn't let Americans gamble with a virtual currency on your site. Does everyone forget what happened with poker? All gambling sites on the internet should ban US IPs. It's not worth the trouble. For satoshidice you can still bet, still get paid, Bitcoin doesn't know your IP. I'm sure someone will create a site that scans the blockchain so you can view "recent bets". That's about the only thing useful on the site. People will post the addresses to place bets. People thinking that it would always be legal for Americans to bet Bitcoins online were being foolish. People getting legal, setting up the site properly, protecting themselves from future legal matters, that's all good. Like most poker sites online, block americans, problem solved. There's a reason WebMoney blocks Americans. It's not worth the trouble.
Maybe, the sum is quite substantial and I think it can threaten mtgox as a business, perhaps bankruptcy? We don't yet know how the market would be without gox. I'd say it's a considerable risk.
In those types of lawsuits, claiming damages it's usually a ridiculous amount. I doubt MtGox backing out cost them much more then maybe a million or two. This stuff usually gets resolved way before a case, I'm sure they'll settle out of court. Otherwise the lawyers end up the only ones making money. Also even if they lost, collecting the money is another matter. MtGox has a number of lawyers, I don't think this puts their business at risk. At least not for years. I'm sure a lawyer who knows more then I can comment on these types of contract disputes. From what I know, CoinLab ever seeing 75m is extremely unlikely. They'd have to win, and a judge agree, MtGox appeal, MtGox lose appeal, and MtGox pay. That's a 5-8 year process.