I can't document my claim about most people who try to track fail miserably at it...but everything I've read and heard seems to point to that. Especially in today's typical shuffles where there are only small parts of the shoe that are easily exploitable. People should not be encouraged to attempt this advanced technique without going very slowly, spending a lot of time at the coffee table with a shoe, discard tray, and 6 decks of cards doing drills such as recommended by the Bishop. Of course some people get to be good at it and some very good at it and the ability to make big bets off the top of a fresh shoe is very good for the bottom line. People do lose money counting cards...but you and I both know that it is a much more basic technique.
I will tell you that ST does not make you completely impervious to barring. You're still moving your bets around and still winning. I've been barred from several casinos (The Mirage is one) while shuffle tracking was letting me make big bets early in shoes with counts that would be neutral or negative to someone counting me down. I know players who have been backed off tracking and key-carding certain games where there is no way the casino could know or understand what was going on. If you move your bets around and happen to win there is a chance you're gonna get thrown out.