Today we've got a nice order: some guy has ordered DataObjects.Net using pretty old coupon code (upgrade from v3.9) providing 60% discount. I tried to find it in Google, but failed - i.e. there is no info about it at our web sites. On the other hand, promo code was really enabled, so discount was provided.
Initially I was thinking about asking him to make a refund and use one of actual coupon codes. Obviously, this idea was really bad - in fact, it's our own mistake, he just found it (probably, occasionally). And Alexis Kochetov proposed a better idea: we must give him additional 10% discount. So we'll prolong his subscription for additional 2 months :)
Of course, the gap is closed now :)