yes, never use your debit card and use only credit cards online, but cash is better for non-major in-person purchases as it's inherently private and anonymous. it's also better for the payee (hopefully a local retailer not a mega-corp), since they don't have to pay the fees. for major in-person purchases, the extra (fraud, warranty, etc.) protections provided by the credit card may be worth the privacy/anonymity tradeoff.