I don't know if the RC5 crypto algorithm is used for browser encryption, but generally a brute force attack is the most resouce-consuming attack and if anyone were after your credit card number they would stand a better chance to succeed by cracking the remote server. AFAIK all major credit card thefts have been made by raiding some company's database of CC numbers. (There are also many simpler way of getting those numbers, but that's beside the point.)
There are many people who have important information that must be kept secret for much longer than five years. This challenge has irrefutably proved to them that for the RC5 crypto, a 64-bit key won't keep their secrets for more than a couple of years. But then again, these people should know all there is to know about cryptos and keylengths.