QFIT said:
It's not just that it is hard to prove. It is irrelevant. By no stretch of the imagination is using your brain cheating. A casino can demand that you not use a device, alter cards or dice, or collude with a dealer. A casino cannot demand that you stop thinking -- just because they aren't good at it.
There is an alternative viewpoint to that, although I don't personally agree with it. That is:
When you enter a casino you accept, and your acceptance is implied when you play any game, that the house has a legitimate edge to cover the costs of providing the facility - and that any device or methodology aimed at affecting the HE should be considered cheating (whether it's overt like the two gents at the Empire casino in London, or covert such as counting cards) and subject to penalties. This viewpoint I found when trawling the web and reading through the forum posts at gamingfloor.biz.
If you accept this it raises two further points - should counting be considered as cheating and sanctioned under Section 42 of the Gambling Act 2005 (in the UK), or should it be more a case of breach of implied contract and pursuable (for any losses incurred) through the civil courts. Proving counting, as you have said, would be nigh on impossible, but if someone was clearly and overtly attempting to count cards (using their i-Phone perhaps?)there may be grounds for a civil case.
Unlike in the States (NJ), this has never been tested in law in the UK and there are no past rulings for precedent. So it's all conjecture on this side of the pond. But it's the sort of thing one of the casino chains might pursue just to send out a message to patrons not to even try it on.
The easy answer, of course, is to stick a CSM on the table. Job done. This does have a cost though which will eat into what are already razor thin margins (we don't have the LV super-casinos as you do in LV & AC, and profits within the main casino chains are modest at best).