I count cards and it is not hard at all to spot the patterns that counters use. The most common counting system follows a very specific pattern that, if used, w

I count cards and it is not hard at all to spot the patterns that counters use. The most common counting system follows a very specific pattern that, if used, would leave anyone following along with an identical count. In response to that count people will change their betting patterns and this is what is generally being watched for (and guarded against, to your earnings detriment, by people that don't want to get caught). More serious counters will work in teams and the casinos can try to look for the signaling that such teams traditionally employ (in addition to betting patterns). Even with counting (at the individual level) you are really only giving yourself a very slight edge and this assumes that all other advantages are being taken (playing a perfect game, playing favorable rules... unfavorable rules are everywhere these days... managing your bets to take advantage of the count without getting caught, having a properly sized bank roll, etc.). Sadly, after all of that you can still get your butt handed to you on a bad night. On the aggregate you can beat the house with counting and all of the above but only just.