The US patent law has allowed such patents for decades.
VP8 was never even properly analyzed, and Google just pretends there are no patent infringements. Which is simply not possible, judging from the similarities to H.264.
The MPEGLA holds so many patents on basic video encoding technologies, a codec as similar to H.264 as WebM simply HAS to infringe at least a couple of MPEGLA patents. I certainly won't encode anything into WebM as long as Google does not provide proper patent research.