Yes, but it has to have some significant effect. For this to happen, the gain from the format conversion has to matter for the porn sites use case, this has to

Yes, but it has to have some significant effect. For this to happen, the gain from the format conversion has to matter for the porn sites use case, this has to be a certain percentage of bandwidth (wonder how that's for video sites), and then the amount of browser who support it (not just advertise it, cf. IE and its PNG "support") has to be high enough. Anybody got some statistics on browser distribution on a major *tube site? I guess we'll see a lot of Internet Explorer there, although it Chrome's "incognito" mode may have found some fans.