Users create accounts. Captcha. Limits on games played per day. Limits on new accounts created by all users in day. Statistical analysis to observe for bot play. There is a point at which the financial rewards for the cheater outweigh the amount of effort required to cheat.
So, as I said before, cheating is minimal in my concerns. The other issue raised by gigitrix could be a problem.
Well, go for it, if you're confident that you can handle these issues it might be a nice opportunity.
My gf plays sudoku on her iphone whenever she gets a chance : there is a market
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