Ok, the topic is #humpday: Make a video!
That's the gist of Facebook's newest app, called Riff, which encourages people to upload videos, tag them with a topic and then invite friends to respond and add content. People can create any topic they want from "#shakeitoff" to "game face."
"Our hunch was that if you could make videos collaboratively, the creative process would be more fun," Josh Miller, a project manager at Facebook, wrote in a statement announcing the new app Wednesday. Facebook's goal is to get people to upload even more to the social network than they already are and, by extension, attract more advertisers.
But Riff isn't the first video app for social. There's also Twitter's Vine, Snapchat and Raptr's Plays.TV,. Riff has the added benefit of already being connected to Facebook's user base of 1.2 billion people -- about one-seventh the world's population -- who log on to the site from a mobile phone each month.
The app is the latest from Facebook's Creative Labs group. Others include; and .
Riff in particular could encourage viral videos like the ALS Ice Bucket Challenge,. Facebook said 440 million people on its site ultimately watched these videos 10 billion times. Facebook clearly hopes to repeat that type of success.
Riff is available for devices powered by Google's Android, as well as Apple's iOS, starting Wednesday.