You are exactly right, which is why adults are covered by OPPA (where the C, for Children, is removed): http://en.wikipedia.org/wiki/Online_Privacy_Protection_Act

As in contract and rape law, people below an arbitrary cutoff age are presumed to be unable to give consent (or to even understand what "consent" means). Once beyond that age, the person is considered to be able to give consent, e.g. click "Agree" on a Terms/Conditions form or use a website with a very visible Privacy Policy link.