+1
Plus with a minimum post count.
This is all well and good, but I'll be the devil's advocate and ask why the developers can't take some responsibility for who gets their promo codes as well? Take the OP for example. A member since August 2009 with a total of 12 posts, 4 of them in this thread alone. I might say that the OP is being more than a bit hypocritical, since apparently the only thing he uses MR for is to promote his apps. If someone else only uses MR to get promo codes, how is that any worse?
This is hardly an isolated case. Developers come here all the time, drop their promo codes, and then never come back until their next set of promo codes become available. If I hypothetically used a promo code, why should I care enough to reply with the code I used when as far as I can tell the OP can't even be bothered enough to check back in their own thread?
As others have mentioned, requesting a PM for a promo code works just fine. In addition to taking the process of obtaining a code to a level that discourages the run-of-the-mill member who trawls the forum for codes, you can be a lot more selective about who gets your code and therefore uses your app. Perhaps this practice is the one that we should be advocating instead of randomly chosen post count requirements. If you are more selective who gets your code, you can also make a more educated guess as to who will give you constructive feedback and/or leave a review. If I wanted people to give me feedback on an app, I'd take
jessica. over a macrumors newbie any day.
edit: I'd also volunteer that if someone actually PMs you asking for a code, you're automatically that much better off giving it to them as it shows they are interested enough in your app to take the time to request it.