https://www.techdirt.com/articles/20180928/14321340736/stupid-patent-month-trolling-virtual-reality.shtml

This month's stupid patent describes an invention that will be familiar to many readers: a virtual reality (VR) system where participants can interact with a virtual world and each other. US Patent No. 6,409,599 is titled "Interactive virtual reality performance theater entertainment system." Does the '599 patent belong to the true inventors of VR? No. The patent itself acknowledges that VR already existed when the application was filed in mid-1999. Rather, it claims minor tweaks to existing VR systems such as having participants see pre-recorded videos. In our view, these tweaks were not new when the patent application was filed. Even if they were, minor additions to existing technology should not be enough for a patent.

The '599 patent is owned by a company called Virtual Immersion Technologies, LLC. This company appears to have no other business except patent assertion. So far, it has filed 21 patent lawsuits, targeting a variety of companies ranging from small VR startups to large defense companies. It has brought infringement claims against VR porn, social VR systems, and VR laboratories.