Earlier this year saw some referrals from a hacking forum from a young gentleman petitioning the cracking community to crack our software for him: http://www.hackforums.net//showthread.php?tid=2148782 (You may have to register to view the thread)
I engaged in conversation with that community briefly and told them a little about us, and asked them what was unfair about our pricing and if they had any better ideas for us.
The response was extremely positive and supportive, and we received some emails with helpful advice about how to protect our program from crackers like themselves.
I've no idea if we got any more sales than we would of otherwise, but we engaged with a community in a respectful manner and it's likely we delayed cracked versions of our software being made freely available.
The problem I see with the OP's method is firstly I would be peeved if I was a legitimate customer and interpreted this post as rewarding bad behaviour.
Secondly as OP has publicly posted this he might actually lose revenue from future customers purposefully entering wrong keys to gain access to the coupon code. If OP redacts this now, customers might be annoyed by this and ask for discounts, or even find alternatives. So it's quite short sighted to post this in my opinion.
Thirdly and possibly most importantly is that it's boiling the company-customer relationship down into a purely financial one. A relationship with a potential customer (no matter what their software ethics are) should be more than that, and it can have unexpected rewards like we experienced.
The message in the OP is disrespectful as well, it's highly accusing (is there any risk legitimate customers could see this?). It's my opinion that these sorts of tactics don't do your company and favours in the long term, although in the short term you might collect a handful more dollars.