"One of the most important properties of my media formats is it's accessiblility."
Great! H264 is what you want then. It's not only supported, but also hardware accelerated, on most devices out there. WebM isn't, and won't be for a long time.
"What business wouldn't pay a slight file-size penalty (to maintain the same quality) in order avoid being bound to some per-seat licensing agreement with all its associated administrative and reporting obligations?"
Every business that would rather pay royalty fees than for extra bandwidth required by a shitty codec. You probably also want the majority of your customers to actually be able to view your content. So there's also that "minor" inconvenience. But aside from that, what business wouldn't go the WebM route, right? :P
"Do the math."
Actually, I'll let you do it.