Ask HN: What do you think of authentication tied to your passport?

I've seen a lot of online games in China and Korea that require users to sign up with their passport number in order to play. This seems like a great way for the government to make sure kids don't play too much.

What do you think of signing up with a passport number to online games and social networks in North America?

On one hand, it seems like a further privacy breach. At the same time, it's a good way to track down anyone with bad intentions. Thoughts?

(I have neither a Chinese nor Korean passport, so if anyone has experience with this it would be great if you can add in any detail I missed.)