I complained to the Isle of Man that Pokerstars does nothing to prevent a child from gambling online, and that they have a responsibility to verify ID at the time of registering a real money account. I received the explanantion below. You can interpret this however you like -- I read it as "we wouldn't mind doing something to keep kids off our member sites as long as it doesn't cost the sites any of their gambling customers or us any of our regulation customers."
Players who arrive at a site want to start playing as soon as they can. If they are slowed down by a registration process that is harder than an unregulated site, they will simply switch to the unregulated site where they can start playing faster. That means more players playing on unregulated sites and no incentive for companies to seek licenses and that’s bad for players. So the issue of up-front registration is a fairly complex one and up-front verification will never stop a minor with access to his dad’s passport from playing.