Ross Anderson: Bot tending might be an attractive activity for children, because children could receive the challenges on their mobile phones, to which they are almost physiologically attached these days, and they're perhaps used to relatively smaller amounts of pocket money. Mike Bond: You talked about routes for sending CAPTCHAs which go outside the game; given that the bot has control of the client, what about sending the CAPTCHA back into the game to a human player who is maybe indifferent about bots, and then paying him a virtual currency to solve it? The client would have both the infrastructure to reinsert the CAPTCHA, and to make a payment, there and then.