I'm a Troll. I buy a company with a IPA-based patent portfolio. The company is on last fumes, but I keep it alive (just). I also pay the ongoing patent fees to keep their patents valid.
My goal of buying this company is to sue a much bigger company with huge valution and profits. So I copy the business of the bigger company and rub their faces in it in every way I can. I am provoking an infringement claim. I happily sell my infringing software to anyone who wants it, including the competitors of the bigger company. I indeminify my customers against patent infringement. Eventually the bigger company gets irritated and goes after someone. Eventually it's me because of the indemnification.
So now I pull out my IPA-based patents defensively. To defend against someone infringing my inventions.
Or am I missing something?
IANAL but this would seem to be a legitimate use under IPA. However, the bigger company's lawyers would undoubtedly know that you have those IPA-based patents, and if they did file for infringement, they would do so on the merits of their own patents. They would never attack your IPA-based patents, so you'd have no grounds to ask for sanctions for a frivolous suit. At this point, you might as well just quit the patent trolling business.
Hmm, it seems to me that if you are buying a company and keep selling the product, you might not be a troll and you might have legitimate business reasons to defend that product from another company's patents....