social media, social networks, video, As expected, Twitter launched its recently acquired video-tweeting service Vine this morning. The mobile app allows users to share 6-second videos directly through Twitter.

The videos display in the Twitter stream in the original tweet, reflecting another round of Twitter’s efforts to become a media website rather than a data stream or a platform that invites third-party development.

Perhaps because of data-hosting concerns, retweets of Vine videos cannot be expanded to display the video. Users are directed instead to Vine’s website.

At least for now, users uploading videos can also share them through Facebook.

Vine’s six-second looping videos look a lot like animated GIFs, but they include more frames and support sound.

Many, including Twitter co-founder Jack Dorsey, expect Vine to be the long anticipated Instagram of video — meaning, they hope it helps video-sharing go mainstream.

Vine is the most exciting thing I’ve seen in a while. Not just because of the team, because it brings an entirely new art form to the world.

— Jack Dorsey (@jack) January 24, 2013