Snapchat, the photo- and video-sharing social media app beloved of teens and young adults, hit an estimated 150 million daily users recently, blowing past Twitter (140 million users) and pulling audience from Facebook’s Instagram, the giant in image-sharing at 300 million users.

Among the features powering the popularity of Snapchat: “Stories”, little video or still image slide shows edited together from Snapchat users “Snaps” and intercut with commercials.

Last week, Instagram struck back, beginning to roll out a competitor to Stories, that it calls…Stories. As on Snapchat, Instagram users will make video and slide shows, and mark them up with funny drawings or text. Like this cat.

Reviews in the computer press are pretty unanimous that Instagram hasn’t topped Snapchat; its Stories is just good enough to keep Instagram users on the property, they say.

“You don’t always need to be better to win, you just have to rob your competitor of its appeal,” wrote Josh Constine, on TechCrunch. “Why would people stray if you provide convenience, even without quality?”

This week, Twitter made its move on Snapchat. The company announced that “Moments”, its Stories, that has been published by Twitter staffers since last year, will open to anyone to publish over the next few months. Twitter also has been testing “promoted” Moments, a sponsored version, with some selected advertisers, presumably with a view to rolling that out to all, as well.

See some Moments examples: Scenes from training camp with the Chicago Bears and actress Bryce Dallas Howard answering Tweeted questions in a series of short videos.

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