Amazon Video
Customers of Amazon Video can stream on the web using an HTML5 player (supported in Chrome, Firefox, Internet Explorer 11, Edge, Safari and Opera).
Use of Ogg formats in HTML5
CTO at Opera Software, Håkon Wium Lie explained in a Google tech talk entitled "The  element" the proposal of Theora as the video format for HTML5:
After the presentation, Lie was asked whether Opera will support other formats than Ogg: