Just clearing up a few things brought up on this thread:
You can't use someone else's credit/debit card at POS in the UK. If you attempt to, the retailer has every right to retain the card and report it as attempted fraud. This is regardless of whether you have "permission" to use it - it would then be up to the issuing bank to decide what action to take. Almost all credit card issuers in the UK can issue a secondary card to any card holder with a different name on it - however, any spending on that card is the primary cardholder's responsibility.
It was always strange in the UK, watching US movies where kids would get a loan of their parents' credit card for a shopping spree!
When ordering stuff over the internet, there are 2 ways it can be authorised - just a normal authorisation with card number, expiry date and CVV security number - if these transactions turn out to be fraudulent, the onus is on the retailer to prove they took adequate steps to ensure it was genuine...
and then there's AVS authorisation, which most sites use these days - as well as all the card details, the full name on the card and the house number and postcode the card is registered to is taken - it is then up to the retailer whether they will allow it to be shipped to a different address than the billing address (most cases it is NO). This is more secure, and any fraud committed this way is easier to track, and therefore will most likely fall on the credit card company.
And yeah, my mum was angry the day the corner shop would no longer serve my sister cigarettes - even though they were for my mum!
