Facebook founder Mark Zuckerberg just signed up to video sharing mobile app Viddy, and he has just posted his first video on the service too.

‘Zuck’, as his nickname there is, posted a video of his dog Beast playing around in his house.

That first entry has already got more than 1,200 likes from other users of the service, though that number could increase massively if Zuck were to share it publicly on his Facebook page, which has 13 million subscribers. A recent photo of the dog got more than 250,000 likes, and Viddy could benefit massively from such exposure.

The Facebook founder recently splashed out $1 billion to buy up mobile photo app Instagram, a service that Viddy is often compared to, and that is sure to get people thinking about the startup and a possible future acquisition.

Viddy has just passed 15 million users, and Zuckerberg’s arrival is sure to help grow that number, and get tongues wagging in the process.

The news completes a busy recent period for Viddy after it raised a round of new funding from rockstar investors that included Twitter co-founder Biz Stone, Skull Candy’s Jeff Kearl, Jay-Z, soccer star Gerard Pique and his partner, popstar, Shakira.

The service isn’t the only one pioneering the mobile video app space, which is being looking at more intensely following the Instagram acquisition, rival Socialcam is growing fast too.

Spun out of Justin.tv last year, Socialcam recently revealed it added 4 million users over one weekend alone. But with Zuck on board at Viddy, it could do with a superstar endorsement of its own in response – may we suggest Jack Dorsey?