don't get me wrong, I understand how gambling works, but aren't certain transactions on satoshidice internal? I wish I had a link to the conversation, but I heard that they plant a certain amount of bets against themselves, again, why, I don't know... anyway, it wasn't me who won, so who cares?
The "why" question is easy to answer. SDice pays the profit to their shareholders. Now when they play internally and win they remove profit of the shareholders and increase their own profit. And winning would be easy because they know the daily secret.
Not saying that they actually do it though.