I say establish a rules set before the start of an exchange - make the rule set transparent and open, with benefits (continuing participation, receiving prints) and consequences (certain APUG priviledges suspended until compliance is verified). Failure to comply would be determined by some set criteria - IE failing to reply to a series of three consecutive messages over a period of three months, or providing a lame excuse (my dog ate the prints... for the third time, I lost the address, etc). Have some kind of three-strikes-and-you're-out deal - someone can legitimately fail to deliver in one exchange, but be allowed to continue participating. A second failure puts them on probation, and a third failure means permanent ban.
I don't think making a public blacklist is necessary, but having a publicly posted policy on how one gets on the blacklist, and the steps required to get off the blacklist, would go a long way to remedying the problem.
I'd also be in favor of creating a set of rules for sending poorly made prints, but that's so subjective a judgement call that I wouldn't want to be the one who has to do it. Someone could send a bad print, then claim (perhaps legitimately, perhaps not) that they are a novice and don't know any better. If you set up a grading system of novice to expert, how do you decide when someone is no longer a novice, versus a lazy slacker, versus just an incompetent printer?