Tom W.

Quite a high APR (but this isn't relevant for how I use credit cards!)

They have a highly objectionable term in their terms and conditions saying that you cannot record their password in encrypted form. This is both objectionable and insufficiently prominent.

They provide you with two memorable words (one for the phone, that you are guaranteed to forget the details of because who used a phone, and an internet one). A single incorrect guess causes them to lock your account and ask you to post them proof of identity and address. Kind of stupid really.

Accidentally fat-fingered an order. I couldn't fix this despite informing the hotel within 10 minutes by e-mail. Of course their terms and conditions (and the law) probably let's them do this, but it's not really in the spirit of things, since my fat fingered order was a booking three weeks later.