I had an interesting talk with the owner of Dr Coffee's Cafe, which as far as I could see on a brief visit is the only reason for Darlington1. She'd not yet actually finished her PhD, on the economics of the coffee trade. If I remember rightly, though, she was rather sceptical about capitalised Fair Trade, saying the registration requirements can actually get in the way of bringing extra value to the original growers and that middlemen take most of it. Instead, she said, buying any premium grade of bean was a more effective way of getting wealth to the workers.
[1] @doctorcoffee on twitter.