Question:

IANAL but isn't it illegal (grounds for a lawsuit at least) to use the image of someone, who is too young to provide legal consent, in an advertisement without their legal guardian's express written consent?

I could have swore that was a thing on a higher than state level but maybe I'm wrong? Like I didn't think you could make a 'settlement' and then legally avoid this sort of thing in the future.

Isn't this quote all sorts of legally indefensible? When did non-adults ever have the ability to 'represent' anything in the absence of their guardian?

any user under 18 “represents” that her parent agrees to let Facebook use her image in ads.