Creatine is sufficiently bulky that blinding would be a pain in the ass (you'd need something like 10 OO gel caps a day, although at least creatine is tasteless in my experience), and it's also very cheap; so I'm not sure blinding is entirely justified on a cost-benefit basis. It may be better to just randomize blocks of 2/3 weeks: it won't eliminate the expectancy or other placebo effects, but it does eliminate most of the potential problems. And just randomizing is a heck of a lot easier.