What prevents people from winning easy by running a card counter while playing?
8 decks are shuffled before every hand. ==> That's what prevents people from counting. It's the same as a continuous card shuffler used at many casinos.
When cards are dealt from a shoe, its possible to count (even with 8 decks, or 1000 decks), you just start at 0, for a low card 2-6 you subtract 1, for a high card 10-A you add 1, for 7,8,9 you do nothing. When the count is high, there are a lot of 10's due up. To defeat this, casinos use continuous card shufflers, ie they shuffle all their decks before each hand. My website does the same thing.
EDIT: I forgot to say, with the link, that shuffling the deck before every single hand is not necessarily a bad thing. It just means that card counting is dead.