It is possible that pirate from BS&T is Dread Pirate Roberts from Silk Road. This would explain why he's got to keep so quiet about what he's doing with the invested coins.
That would mean it's not a Ponzi; it's simply profiting from the Silk Road mixer service. Assume that that this is the case. It would mean that BS&T is not a scam. It doesn't mean it's risk free though.
That couldn't possibly generate 3000% yearly returns.
It's a ponzi scheme. Ponzi schemes unravel slowly, since the investors (victims) tend to be very loyal. At 7%/week, even if no one new invests and everyone who has already invested just withdraws their profits, it takes 14 weeks to go through all their money. Usually most victims reinvest and many new victims come in, so the scheme can go on for an extended time.