Understand online gaming industry.
I am not sure about number but online gaming industry is about 7 billion dollar industry. I am not sure about number but I am sure that it is billion dollar business.
That is a lot of money!
So casinos make lots of money, and they don't have to cheat you to make money. Why would they risk their gaming license that is very expensive, when they already make so much money?
Safest way to go is to play in big casinos. Big casinos are well know, everybody plays in them, therefore they have good reputation and they just doesn't have to cheat you, they already make millions every day.
STAY AWAY FROM SMALL CASINOS. ESPECIALLY CASINOS THAT HAVE SERVERS ON LITTLE ISLANDS IN CAREBBEAN. Most small casinos can't afford expensive gaming license, in countries like Canada, and most European countries. That's why they pick countries where is cheap to get gaming licenses. Most of these countries have corrupted governments and internet casinos can do whatever they want. And your money security is NOT guarantied.
Exemption of the rule is Gibraltar (south Europe). The best internet casino 888.com or casino on net has its servers there.
Whether you are playing for "real" money or "play" money software IS THE SAME.
Yes casino employees can always see how much you lost or won and I think that all casinos reserve rights to deny service to anybody.
My picks for good reliable casinos are
888.com
pokerroom.com (poker room and casino)
if you like poker
partypoker.com