Today YouTube announced 60fps support will be coming “soon”.

For us interested in high-motion video games, this is the
biggest news since the introduction of HD on YouTube (720p in November 2008, then 1080p in
November 2009 – though 720p was more than enough for upscaled Mario Kart Wii videos at the time as the game is 480p native).
Look ahead: creator features coming to YouTube (Thursday, June 26th 2014)
• 60 (yeah, six-zero) frames per second: Your video game footage with crazy high frame rates will soon look as awesome on YouTube as it does when you’re playing, when we launch support for 48 and even 60 frames per second in the coming months. Take a look at some preview videos on the YT Creator Channel. Make sure you’re watching in HD!Browser support is ambiguous… Chrome should display the example videos in 60fps as long as you watch in HD 720p or 1080p, but Firefox apparently needs HTML5 player ON or something. Anyway, it should be pretty obvious whether you're seeing the 30fps or 60fps video.
While it will allow people to watch videos as smooth as the game, it requires more bitrate than 30fps for the same quality (about +25%), which means bigger files/longer uploads, longer encoding (+50%), but the thing I'm more concerned about is the final quality on YouTube. The website is known to harshly re-compress videos in order to save bandwidth, which results in high pixelation aka shit quality for high-motion videos with lots of details, sharp edges and colors which is EXACTLY what Mario Kart 8 is.

Original video:

Rainbow Road is the worst case scenario but it also applies to a lesser extent to Electrodrome, Thwomp Ruins, Mario Kart Stadium and DS Wario Stadium according to my tests. If it already looks that terrible in 1080p30 on YouTube, it'll look even worse if YouTube starves 60fps videos in the same manner.
NOTE: It remains unclear whether this feature will be available to everyone, or only “Partners” i.e. people who monetize their videos. The terminology used on YouTube's blog is a bit confusing (talks about both “Creators” and “Partners”).