I'm on minecraft chatting with murderscene & dooglas about the provably fair betting. What I'd like to see is the sha256 of each game's "secret" *before* I play.
So, you could shuffle the deck, take the sha256sum, and write it in the blockchain the day before you use it. Then you take the user's lucky words, reshuffle accordingly, and play the game. On the results page (bitvegas.net/....) you can show the whole process which is verifiable.

EDIT: this allows the user to know that the original shuffle was generated before the game was played.

See http://btcmultiplier.com/keys.php for how they wrote a 40 year list (!) of sha256s into the blockchain with a single transaction.

Edit2: I'm just thinking, it would be far better to use a public source of entropy. For example, assuming a 3-player game in which no-one says any lucky words (or some people say predictable lucky words), what's to stop a casino from tending to favor decks with top cards: A,2,5,8,K,4,6,9, so that the dealer gets A & K blackjack! So the deck should be reshuffled with a random number just before the game, but that the random number can be proven to be outside the control of the casino.  e.g. btcmultiplier use the transaction ID.

In short, I'm saying that, assuming bitvegas is using, and not filtering in it's favor, a good random number gen, then the fairness is provable. It would be great if you could also prove the randomness.

Any thoughts?