[notahacker]

In general, using credit card details as a form of identification is a bad idea since it's exactly the sort of behaviour phishers and scummy "free sample" rebillers are trying to encourage. These attack vectors are much less successful if the median internet user believes "anybody asking for my credit card details when I haven't agreed to pay for something is a scammer"

[DanBC]

That's a good point.

Assuming the filters stay: what's a reasonable method to check age?