they need more than the spread
Very true that the computer used with RFID table systems will show the spread but it does not correlate it to the count unless another step is taken.
I think shufflemaster or one of the other firms that makes it's money by selling greed and paranoia to casinos, has a system that similar to mindplay, uses a reader and marked cards along with RFID chips. Do not know if it is up and running yet or just in development. This would cover the additional step needed and would also be subject to the use by casinos to cheat players.
I do believe that once they can develope one of these systems to the point that the average player does not even know it is there and it does not slow down the game, it might become effective. One of the biggest factors that has worked against things like Mindplay and CSM's is that even a player who might be a pure ploppy and play some very bad games, feels that there is something wrong with strange gizmos on his table and will go elsewhere to play. Since these are the people who do donate to the casino's profits, their fear (without knowledge) of these things has been a huge factor in their failures.