Actually, upon further thought, this is only partly correct. AMEX and Discover do have their own banks (American Express Bank and Discover Bank) so I presume that if I default on a AMEX-only balance or a Discover balance, AMEX or Discover take the hit. But for any Visa, Mastercard, or bank-issued AMEX balance, which make up the lion's share of the credit card universe, it's the issuing bank that carries the consumers' debt, not the credit card company.