A small firm in Arizona had 14 computers, and bought a license for Avast! Pro covering those 14 machines. They got a license key, which ended up on warez websites, where it obviously started spreading like wildfire. Avast noticed how the license key was being used by many more users than just the original 14. However - instead of killing the key, Avast let it run its course as an experiment.
"We found our licence code at a number of warez sites around the globe," said Vince Steckler, chief executive of Avast, told PCPro, "There is a paradox in computer users looking for 'free' antivirus programs at locations with a known reputation for spreading malware."
The result is pretty staggering. Within 18 months of the key appearing on warez sites, it had already been used 774651 times (the article notes 774651 people, but that's nonsense; the number of people is most likely much smaller than that), in 200 countries, including the Vatican. An Avast! Pro license goes for €33.57 (excl. VAT), so theoretically, Avast just lost €26005034.07 in revenue. Of course, most of those people wouldn't have bought Avast! Pro if they had to pay, but still.
It's especially idiotic since Avast has a free version as well, which would likely cater to the needs of most of those 774651 installations - in other words, Avast is a modern software vendor taking the needs of their customers and the market into account (unlike some other industries). Pirating their stuff is not only against the law, it's also entirely unnecessary.
Avast is actually being a good sport about this. I'd say they are perfectly within their right to block all those installations, but instead, they're offering users of the pirated key the option of going legal - by buying the Pro version, or downloading the free version. Some conversions have already been made.
Turning lemons into lemonade. You're doing it right.