Same idea but I would not say it like you: - social network site will ask Google if the use is old enough with any random I'd that can be used to match Google

Same idea but I would not say it like you: - social network site will ask Google if the use is old enough with any random I'd that can be used to match Google response. - but Google will now have a record of your Google account requesting age verification to access a social network / porn website... - also, if anyone can open a Google account with the name John doe, the age verification will not have any sense. - so Google will be required to check your identity, and so will require a government issued id in the end. You can say that Google will just rely on some other third party, like a bank or phone provider, but in the end of a chain there will still be the gov id to be used.