I've heard of big gambling cases and it happened several years ago an entrepreneur cooperates with casino owners to carry out money laundering
In another story I also heard about the genius promotion of an online casino so they don't spend a dime on promotion but everyone talking about the casino is even published in the online news, so the team from the casino makes big bets or wins big to attract the attention of other players and become a conversation in various gambling communities.
I'm not saying Bitcoinerz does that, it's just knowledge.
I understand your concerns but I believe Stake has got enough reputation here so not to conduct such shady things as in the end, it came out as Primedice's sister site and PD had been there for over years paying its users any BTC amounts if they never cheat the site.