Check out my experience at betfair casino:
I deposited 70euros and started the wagering for the 75euros bonus. I played single deck blackjack 1-2 euros each hand, basic strategy, and without ever by balance exceeding my initial deposit, I kept losing and losing. Lost my deposit and had to reload. Results after I completed wagering:
hands=893
average bet=1.38 euros
profit/loss=-76.5 euros
Now when I had completed about 750 hands, I was 98 euros down.
How certain it is that I was cheated? I found an easy way to answer this:
I use this calculator for estimating risk of ruin which refers only to the number of hands:
http://www.card-counting.com/blackja...culator-c3.htm
I was not flatbetting but changing my bet between 1 and 2 euros. However, as a rough idea, with that calculator you can get the probability that someone who has a bankroll of 98/1.38=71 units, will get ruined-bankrupt after 750 hands. I did bet about 10 euros once and lost. So exclude this 10 euros bet I made, and suppose this was a bet of 1 euro. So, calculate the risk of ruin for 62 units of bankroll after 750 hands. (house edge=0.3%, standard deviation per 100 hands = 11.3)
The risk of ruin for these values is 5.21%. That much I had for what happened. Bad luck? I would think so too, since when playing too many bonuses, this 5% naturally it will happen, but how often? Almost the same thing happened to me to quite a few casinos.
You are doubting whether they would cheat for millions of dollars, whereas they cheat for a few dollars. Of course these few dollars multiplied by the number of players, is thousands.