For reason discussed below, "card counters" make their money by observing the flow of cards as they leave the deck. This is legal in most cases (although it's a felony to use a "device" such as a computer in Nevada). It is frowned upon, probably because it violates an unwritten rule (the house is supposed to win).
Because the rules of the game (the deal plays after all the players), the casino will win the majority of the hands. But there are several offsetting rules that reduce the house edge to about 1%:
1) Players are paid 3-2 for blackjacks (more like 5-4 nowadays), unless the dealer also has a blackjack, in which case it's a tie.
2) The dealer has to "hit on 16, stand on 17." Players are free to make better decisions.
3) Players can "double down" in advantageous situations.
4) Players can "split" two equal cards if it is to their advantage, essentially doubling their bets, and getting two potential blackjacks for e.g. A-A.
Card counters do one more thing to tip the odds in their favor. There are rare situations (when a lot of small cards have come out of the deck, leaving a disproportionate number of ten valued cards). At such times, the game is actually in the player's favor ( 1) greater potential for blackjacks, and 2) greater potential for the dealer to bust.) Card counters will "bet big" at such times, and "bet small" at others. The bet size variations (typically 5- or 10- to 1, larger than that of a typical "tourist), help identify a card counter. If someone were to "flat bet" (bet the same on every hand), card counting probably would be useless.
Nevada casinos will typically bar (eject) or harass people identified as card counters. (Following a court case, Atlantic City casinos can't do this, but will merely "shuffle up" after every deal to eliminate the counter's advantage.)
IMHO, Nevada casinos shouldn't be allowed to do what they do, but should have the privilege of "money managment" available to every player. If casinos had the right to limit bet sizes, and more importantly, bet VARIATIONS to say 2-to-1, it would be roughly even money against the best card counters (and make money from a bunch of wannabees).
Is this a workable solution for the casino to not lose money at blackjack? Would this be "fair" to both the house and players?