all of the hostility around here really surprises me. these exchanges are a great idea. i just joined in one, and have already fulfilled my "obligation". all this talk of being "owed" a print seems to be getting nasty.
if you're going to sign up, then you might as well participate. if i don't receive a print, i'll be upset. i put some time and effort into making the prints (i sent two to my recipient), not to mention the five bucks it cost to send the package from the states to the UK.
by signing up for an exchange, you are making a commitment. maybe there should be a clause posted - if you sign up, flake out and fail to send your buddy a print, we'll arrange for a jailhouse style tattoo that reads "I'm a slacker" to be placed on your forehead, backwards of course, so you can read it in the mirror.