Despite being based on Android, a Facebook phone would be competition for Google as much as it is for Apple. Google benefits from ad revenue tied to their search and other services which would likely be supplanted by Facebook services on a Facebook-based phone.
Facebook to Enter Mobile Phone Market in 2011 – Mac Rumors.
I wonder if Facebook devices, or Verizon Bing devices will be counted by Google as Android activations.
See also: asymco | Is a Facebook phone destined to be a Vanity smartphone?