It's the MPEG-LA who needed to put up or shut up, as you put it. Vague threats of assembling a patent pool, a threat that never materialized, are not evidence of infringement. I'm inclined to believe that the deal with Google this late in the game indicates that MPEG-LA didn't have a leg to stand on, as while they were negotiating with Google they could have gone after Mozilla or other VPx users.
I think this story sounds like great news. MPEG LA's licensors include the research labs -- Fraunhofer, etc -- not your usual patent trolling companies. This gives the labs a sugar daddy (Google) that has a commercial interest in paying them for it their advances to be licensed to the public. Which is a nice release valve, because government budget squeezes means there's always more and more pressure for research labs to lock up their tech to earn money from commercialising it. Good on Google for doing this.
