Working with Booking.com as an affiliate over the years I have experienced so many broken things and a sheer indifference / ignorance from the company. For instance, their referral program was long abused by scammers who would place a hotel booking using stolen credit card and then claim 5% cashback via numerous online cashback services. Book a €5000 resort stay using someone's else card and get €250 out of it almost risk free. Fraudsters with the IP addresses from Palestine were happily exploiting this and Booking's anti-fraud systems were largely non-existent..