This is certainly a bad idea. The last thing you want to do is get into a battle with crackers. They have far more time and expertise at cracking software than

This is certainly a bad idea. The last thing you want to do is get into a battle with crackers. They have far more time and expertise at cracking software than you do at stopping them. For this to work, the intentional bug would have be small enough not to warrant "fixing" by the cracker. In other words, it's unlikely to make a difference. It's better to think about why people pirate software. A large proportion don't have the means or inclination to buy, so let's disregard them completely. The remaining group could buy, but for whatever reason, do not. If piracy is easier than purchasing the software legitimately, you've got a problem. Ideally your store should be one page, and require as little information to be entered as possible. Multiple payment methods minimise the chance that a customer won't be able to complete the transaction. PayPal makes impulse purchases easier (assuming you're at that price point). To sum up: You're probably not losing many real sales to piracy. In the cases where you are, you won't restore them by adding layers of "protection", but rather by looking at why someone might chose to pirate in the first place, and fixing it.