The question of online gambling cheating is more complicated. While playing blackjack, casino is considering player as a fraudster if player counts cards or uses mathematical formulas in order to win. At real casinos card counting professionals have to skillfully hide their actions and strategy from dealers and managers. Online players are not monitored by anyone; they can write down what cards they had and even use computer programs to make the game easier for themselves.
Some online gambling sites offer players graphs that display mathematical tendencies of blackjack card dealing. In this case, cheating becomes so easy that nobody thinks of it as cheating.
On the other hand, other hidden methods of getting advantage at a casino are simply impossible to apply online. There's no chance to mark cards while playing video poker or put a magnet ball inside roulette wheel. Cheating at online casinos requires hacker and programmer skills to rewrite gambling program. And although that is basically possible, it's unlikely someone can make it and not get caught.
Changing gambling games coefficients affects not only results of a fraudster, but every user. Gambling website administrators will quickly find out that something went wrong and would cancel the game.