Facebook's CEO has denied a "Facebook phone" in the past, and to some extent these developments don't contradict that. Instead we'll see "dozens of phones with much deeper social integration than anything we've seen so far."
The global social networking site already has its mark (no pun intended) on most smartphones and featurephones either via optimized mobile apps or the mobile Facebook site. As much as I use Facebook myself, the app is enough for me.
However, younger mobile phone users will likely enjoy having a dedicated Facebook button. Let's just hope that the mobile devices that sport Facebook buttons will have enough other useful features to back them up.
To zee Zuckerberg speak for himself, check out the video below: