Nokia 808 supports up to 32GB micro-SD
After a question in the club I asked Nokia's product manager here in the Netherlands wether or not the Nokia 808 PureView would support a 64GB micro-SD card. Well, I checked, they checked and probably someone else checked also - and you've already read the answer.
Nokia garantuees a 32GB micro-SD will work, but they will not garantuee the same for the 64GB size. That is not to say that it won't work at all for sure, there is just no garantuee it will. My own card is a 32GB version, I don't have a 64GB card to test it. By the way, I think using USB-on-the-go is just as easy if you have a storage problem.