Google Android tried in this way with Flash player support, according to the Adobe Flash WebM via hardware accelerated soon be able to play. iPhone & Co left out, simply because no Flash ... Only the point.
WebM include Google, synonymous and when to distribute the free, they give their users - as opposed to h.264 - precisely a license, the license that protects against claims.
Since h.264 the development of all industry sizes bundles is fairly certain that this pool their patents are infringed, and that royalties threaten.
As for the open standard: WebM has an "open license", but just not in the details disclosed, while H.264 is an ISO standard, but is just a license with the proper permissions.
This is again a crappy fight for standards that will be fought on the backs of the user.