Facebook is embracing what is likely to be a controversial addition to its popular social networking site: video advertisements that appear – and automatically play – in your Facebook "News Feed."

In today's blog post announcing the new ads, Facebook calls them a high-quality way to let advertisers "tell their stories to a large number of people on Facebook in a short amount of time." Facebook says the launch is the beginning of a test, leaving open the possibility, however remote, that the ads might change in some way – or get canceled entirely.

The News Feed is where Facebook users get updates on what family and friends are up to. The ads will begin playing as soon as they scroll into view, although they will be muted. Clicking the ad will activate sound. Facebook writes that "if you don’t want to watch, you can simply keep scrolling." A spokesperson tells us, however, that the company will also offer a pause button.

In its news release, Facebook frames the video ads as a way to help “brands tell stories on Facebook to ensure the best experience for people.” In prior earnings calls with Wall Street analysts, Facebook was more forthcoming about the profit potential behind these videos: Company executives made it clear that advertisers were pushing them to explore such ads.

"We’re seeing really strong results," Facebook COO Sheryl Sandberg said of a precursor to the video ads in a call this past May. "Because of that, and because of marketers inherently liking video as a format, we continue to explore new things.

She added during a July call: "We see a lot of marketers using that [precursor] product and seeing good results, so the demand to do more in video on Facebook is there."

Advertisers got a taste of the potential for video ads when they were allowed to attach videos to their Facebook "Pages," thus inserting the videos into the news feeds of people who voluntary follow the advertiser on Facebook. Unlike those videos, the new video ads, known as "Promoted Videos," are designed to reach a large number of people, such as those who do not follow the advertiser on Facebook.

Facebook shareholders, including staffers and executives with stock options, have their own reasons to like this product. Advertisers are expected to pay a significant premium for video ads, lifting Facebook’s financial performance and buoying its stock, which was trading below its initial offering price until this past fall. Today, the stock is trading up roughly 90 cents to around $54.70, a 44 percent premium over the initial offering price.