My dad swears that the casinos cheat. Lots of losers swear they cheat too. But here in reality, it's almost a certainty that casinos do not cheat. The casino industry (at least the land-based casino industry here in the USA) is highly regulated industry. A lot of casinos are public corporations too, and Martha Stewart demonstrated for us the danger of cheating when you're part of a public corporation.
But the main reason I'm so confident that the casinos aren't cheating is because I understand that because of their inherent, unbeatable mathematical advantage over the player, they don't have to cheat to win. They're going to win anyway.
And honestly--if someone dishonest were working at a casino, wouldn't he be more likely to rip off the casino than the player? Because who's got more money? The casino, or the player?
Now let me address online casino cheating separately. Do online casinos cheat? I still don't think so. Again, they don't have to. And if you're smart, you'll only be playing at an online casino who is licensed by a gaming commission in their country of operation.
But online casinos are no different than land-based casinos in this one fact: the house has the edge. They don't have to cheat.
The most common legitimate complaint you'll find on discussion board for players is that they're having trouble withdrawing their winnings. This happens often enough that it is a concern, and it should be a concern. Casinomeister keeps a pretty good list of rogue casinos on his site, and his forum generally contains pretty good info on who the troublesome casinos are. You can also do a search on the forum at Winner Online for the casino name. (It's also important to note that we don't promote casinos on this site who have a history of not paying their players. You can gamble at the casinos on this site with confidence.)
Just remember to take some of the player complaints with a grain of salt too. Not all players are honest either.
But for the most part, you don't have to be concerned about cheating casinos, be it online or land-based. And the casinos I advertise on this site are trustworthy. If they're not trustworthy, or if something comes up to make me believe otherwise, then I pull their ads down.