As a past member of Met-Art and current member of Digital Desire, I would think that this has the potential to save lots of bandwidth for those types of service

As a past member of Met-Art and current member of Digital Desire, I would think that this has the potential to save lots of bandwidth for those types of services. And even the services that do specialize in videos usually offer photos sets of shoots, so it would still benefit them as well. The trick will be to build enough mass to make it common enough for all the browsers to support WebP. I can see Firefox and Webkit adding it fairly quickly, so the real question is, if and when will Microsoft support it?