Facebook has sent out an invite reading ‘come and see what were building’ for an event on Tuesday at its California HQ. But what could they possibly have to show us?

The message has yet again fuelled speculation that Facebook will releases its own handset, despite Mark Zuckerberg denying this last year. At the time, he said: “Building out a phone wouldnt make sense for us to do.”

But, then again, Apple said they would never do an iPad Mini.

What are they building?

The company recently started testing a VOIP calling function in its apps, and with Facebook Messenger, along with its Instagram photo-sharing app, a completely OTT handset wouldnt be out of the question.

The social giant is still struggling to monetise its inventory and saw a huge backlash at the end of last year for suggestion that they might sell users photos on the Instagram app bought by the company. At a TechCrunch event in September, Zuckerberg promised to extend the company’s offering into search, while mobile display has also been gaining pace in recent months. Could Facebook be about to reveal the most well-targeted ad network the world has ever seen?

Whatever it is, it seems consumers are beginning to tire of the ‘always on’ nature of their Facebook selves. A top 40 list of New Year’s Resolutions commissioned for LA Fitness saw Facebook specifically named twice: ‘16. Spend less time on Facebook’ and ’21. Socialise more in real life than on Facebook’. Could Facebook be overstretching itself?