FutureBlock offer and example seems to violate No Arbitrage Rule
It is a well-known observation that Bitcoin exchanges are not efficient (in the academic sense of well-approximating what you call the No Arbitrage Rule). The reason is simply that there are real world barriers that academics usually assume not to be present. If you do consider the risk associated with depositing funds at a Bitcoin exchange, there is an obvious reason why someone would demand a high return for taking such a risk. If you look e.g. at the difference in exchange rates between big exchanges (try Mtgox, Bitstamp, BTCE) you'll see that a difference as large as 10% can persist on the timescale of a year.

The risks include having the exchange hacked and leaving it unable to return your deposit (have a look at Bitfloor) or having its bank accounts frozen during legal investigations and hence unable to return your deposits during the first 6 month or so (check bitcoin-24.com). And then there's the combination of it all with (presumably) enough reserves not to shut down the operation right away (e.g. mtgox). And that's not even considering the risk that the operator is dishonest and gets tempted to defraud customers...

On top of all this, consider that even moving Bitcoins around is not instant. You run the additional risk that during the transfer time the situation changes (e.g. a crash in Bitcoin exchange rate). And the transfer time between bitcoin trading sites can be surprisingly long, since some legislation (e.g. anti money laundering) typically seems to compel them to insist on verifying your identity. This process may, depending on the site, occur in a somewhat surprising fashion, so you never know if they will instantly, or at least within the first days, allow you to continue accessing your bitcoins (or real money) that you gave them.