Here's an excerpt from bj21.com newsletter. The article titled "Casino insider tells all...."
But card counters have to be really good: One mistake an hour could swing the advantage back to the house. And casinos don't mind that. "If you're not perfect at card counting, you can still lose money," Jonas said. "They'll watch you count cards and if you make any mistake they'll just let you play."
If casinos don't mind, why do they tap low level APs with tiny EV's?