DOB, gov't license, Tax ID/SSN, Credit bureaus, right to reject account and close...
Not everyone likes Bitpay or Coinbase as a solution. Especially as states start creating laws that require web owners to have a "bit license" or similar.

Bitpay TOS Section 2.1:
We may require additional information about you (including any person signing below or otherwise agreeing to the Terms on behalf of the merchant) such as, for instance, your date of birth, tax identification number or government-issued identification, and we may also obtain information about you from third parties, such as credit bureaus and identity verification services. We have the right to reject your account registration, or to later close your BitPay account, if you do not provide us with accurate, complete and satisfactory information.