Facebook is testing a new way to push auto-playing video at its mobile users, a precursor to its all-but-inevitable introduction of video advertising. 

Videos embedded in Facebook NewsFeeds will now play automatically, but silently, as smartphone or tablet users scroll by. Clicking on the video will enlarge it and play audio. The test is currently limited to what Facebook calls a "small group of U.S. mobile users."

Only videos posted by individual Facebook users, including those from Instagram and similar applications, will play automatically. Links shared from YouTube, Vimeo and other outside services won't play in line.

Teeing Up Advertising

The initial test also won't include advertisements. But Facebook notes in its blog post that "[o]ver time, we’ll continue to explore how to bring this to marketers in the future."  In other words, auto-play mobile video does indeed look like a way to accustom users to auto-video so that when advertisements appear, people will be more inclined to watch them.

Earlier this week, Facebook CEO Mark Zuckerberg said that mobile users spend one-fifth of their total time on mobile devices using Facebook, adding that Facebook derives more than 40 percent of its revenue from mobile. Mobile video advertising would be an obvious way to mint some additional coin from that trend.

More Video, More Data

Users, however, might not be happy with the auto play feature. Auto-playing video will presumably drive up mobile data usage, which could be a problem for people on capped data plans. There's a big difference between taking the data hit to watch a friend's cat video and finding yourself subjected willy-nilly to a skateboard video shot an acquaintance's son—much less eventual toothpaste or car commercials.