More importantly, a high dropout rate suggests that there is something about the diet that makes six out of 20 people disinclined to complete a three-week study.
Lack of willpower?
Seriously, if you're going to take people who aren't into the whole paleo idea and throw them in at the deep end, they're bound to struggle with keeping on track.
To me its a no-brainer that Paleo is the way to go. How can a diet comprised entirely of nutrient dense food be a bad thing?
I don't need a study to tell me that scrapping the processed crap and empty foods from my diet is going to make me healthier and I'm certainly not going to listen to an article that says the opposite based on one poorly designed study.