In my opinion, instead of putting energy in dealing with piracy, the energy should be put in making the addons more awesome and provide support. Of course you lose money when someone pirates an addon, but you can compensate the loss by making people appreciate your work up to the point where they are morally forced to pay for it. If people really appreciate something, they are gonna pay for it. And if not, make them pay by showing them how awesome you are.
It's just like with Open Source addons of CMSes. Take Joomla for example. Most commercial addons of Joomla are GPL licensed, meaning they can legally be shared by everyone. And yet the developers make a living of selling and supporting those addons. They even advertise their addons of being GPL licensed. Why? Because people would rather buy a quality product with top-notch support than pirate a possibly altered copy. And lets face it, most of those who pirate addons don't have faith in their own forum. They know they will never have a successful forum because if they don't think it's worth spending money for their projects, they won't. And if by any chance their forum become successful, they will realize sooner or later that they need to get stuff the legit way to secure the future of their project.
Those piracy discussions are not a good idea in my opinion. Because piracy can't effectively be stopped, they easily could lead to frustrations and ultimately affect legit users. SimCity debacle, anyone?