Facebook CEO Mark Zuckerberg said Thursday in the company's first-ever earnings call that "it wouldn't really make much sense" for the social networking monolith to build its own smartphone.

A "Facebook phone" has been rumored for sometime, however — and many analysts regard its appearance as a matter of when, not if.

So what's the evidence that a mobile device based entirely around the social network is on its way?

Back in November of last year, the scuttlebutt originally reported by All Things D was that Facebook and HTC were working together to develop a phone codenamed "Buffy" that would hit store shelves in 12 to 18 months — as soon as this coming fall.

Buffy was said to run on a modified version of Android, tweaked heavily to revolve more prominently around Facebook and HTML5 support.

Then The New York Times reported this May that Facebook had hired "more than a half dozen" former Apple engineers who had previously worked on the iPhone or iPad to help build hardware for a Facebook phone. Finally, a Bloomberg report earlier this month reiterated much of what ATD reported in November, but pegged the mysterious "Facebook phone" launch to mid-2013.

The anticipation has grown so great that some designers have already began mocking up Facebook phone concepts (see gallery below).

While Zuckerberg denied the logic of Facebook building a phone, there are plenty of reasons why doing so would, in fact, make a lot of sense.

Facebook has been widely criticized for struggling to adapt to an increasingly mobile web, which most analysts see as dominating the emerging wave of digital life. One hedge fund manager recently predicted that Facebook's mobile sluggishness would lead to the company virtually disappearing by the year 2020.

A Facebook-centric operating system — on a Facebook-branded smartphone — could go a long way toward capturing more mobile users and ad dollars.

So have all the rumors simply been hot air and will Facebook instead focus its efforts on improving a widely maligned mobile app? Or is Zuckerberg simply hedging his bets with some tricky wordplay, and a Facebook phone is in fact on the way? Let us know your take in the comments.