If you've discovered a great video site with lots of good, fresh, pissy content that we don't already support, we will do our best to add it!
1. Start a new thread in this forum for your request (only one thread per site - if it's already been requested join that thread and bump it). Include the domain of the site in the thread title and message e,g somedomain d-o-t c-o-m (hyphened like that because we don't allow link posting in this forum at the moment). We'll try to accommodate all we can, but if others bump your post it will get further up the list!
2. The site must actually host the videos and provide embeddable versions - if their domain or own CDN domain is in the embed code, then they do most likely host the videos.
3. The quality must be worthwhile! Their embedded videos should not sprout loads of popups, too many ads, malware or anything else that will ruin the viewer's experience. This is quite hard to know until embedding is tested and can also be different on different devices. The video should also, for the most part, play in the player and not redirect the viewer away. Their embedded videos must be able to play 80% of the time without stopping and buffering.