Almost a decade ago, OK Go posted a goofy, one-take video of the band dancing on treadmills.

That viral sensation helped re-invigorate the music video world while giving a big boost to a fledgling video streaming site called YouTube. Since then, the band has used YouTube to introduce a series of increasingly ambitious videos (mostly riffing on that one-take vibe) and develop a global audience.

So it was quite a shock yesterday when the band debuted its new video…on Facebook.

While the choice may have been largely symbolic, the band’s decision reflects the growing momentum of Facebook video and the growing intensity of the social network’s rivalry with YouTube. There is still a lot of debate about just how fast Facebook video is really growing and how those numbers compare to YouTube’s.

But here we see a major YouTube pioneer watching the trend unfold and deciding to switch allegiances. At least for now.

In an interview with AdWeek, lead singer Damian Kulash explained:

“With each video, we’re trying to find a new creative challenge for ourselves, and the launches feel the same way. The stars aligned with Facebook this time, and we were excited to try something new.  A decade ago, we fell into a great thing, making our own videos—we found both a new creative outlet and new connection direct to our fans, but it was only possible because we were willing to experiment with new ways of reaching people.”

Here’s the video, which was shot in zero gravity: (note: I and others have reported occasional problems getting the video to play all the way through, even after trying different browsers.)

OK Go didn’t totally blow off YouTube. They posted this video promoting the new official video. But the text below this short video has a link taking users to the video on Facebook:

Though it’s not entirely clear why the band felt if had to choose one platform over the other, doing so could be an experiment to see how well Facebook monetizes the video compared to YouTube.

As AdWeek notes, the band’s management has complained in the past that the ad revenue its gets from the millions of views it generates on YouTube is “like finding change on the street.” If the band sees much bigger bucks from Facebook, that will likely steer a lot more artists and creators away from YouTube and toward the social networking giant.