then tell it in the overt ponzi scams threads.

looking at the very stable price differentials between major exchanges (especially btc-e vs. the others) I'd say that this may be legit.
if they end paying much more than getting in debt themselves to run the arb., the plus side for them is that they unload fully the risk on investors if something goes south.

Moreover the actual interest paid is lower when you consider the fees like the 5% to make a sum available to be wired in their overcomplicated wallet.