Menlo Park, Calif. - If "60 Minutes" were being dreamed up today, its producers might very well have ditched the idea and gone with "6 Seconds" instead.

That's the maximum length of the videos on Vine, a mobile application owned by Twitter that has grown like one of those creeping plants, to close to 20 million users since it sprouted five months ago.

On Thursday, Facebook introduced its own short-video service, built into Instagram, the popular photo-sharing app that Facebook bought last year. The new feature, which is available now, allows users to record up to 15 seconds of video, enhance it with filters and post it immediately.

"We've worked a ton on making it fast, simple and beautiful," said Kevin Systrom, co-founder of Instagram, at a news conference at Facebook's Silicon Valley headquarters. "What we did to photos we just did for video."

The move underscores how video has increasingly become critical to companies like Facebook, which is seeking ways to keep its 1.1 billion users entertained and engaged-particularly on their mobile devices. Video also represents a lucrative and fast-growing area of online advertising, with revenue in the United States expected to top $4 billion this year, according to the research firm eMarketer.

"Sharing video is inherently mobile," said Gene Munster, an analyst with Piper Jaffray. And Facebook needed to get into the game, he said, adding that the company had to "check that box to remain relevant to their users."

Although neither Vine nor Facebook's service is currently offering advertising, it would be easy to sprinkle a sponsor's video ad into the legions of user-generated videos, much as both services do now with text ads in their users' feeds.

The simplicity of both apps-press your finger to the screen to record, lift it to stop and click to publish-makes it nearly as easy to share a video as it is to post a photograph. Still, the biggest challenge for both Vine and Facebook's new service is that video-sharing applications are inherently harder to use than photo-sharing applications.

"Taking a photograph and applying a filter is something that is very easy to do-with a few clicks, it's done," said Brian Blau, an analyst at the research firm Gartner. With video, "the level of complexity goes up," he said.