Adding to that point, there's really no way Google can enforce it. Unless someone openly states it, or Google tracks each IP to see if they use Facebook or youtube (which is illegal), it's not conceivable for them to figure someone's age out. I mean think about it, schools use Google all the time. Mine does. I use it too, and I'm obviously under 18. I understand perfectly well that it's there for legal terms, but even in the event that they are required under law to enforce this policy, it really isn't practical to do so.