Ask HN: Facebook browser?

Many online giants have created browsers after establishing a significant presence or before in some cases (ie. Netscape, Aol, MSFT, Google, etc.). Has anyone heard of, or do you all see potential for Facebook to follow this trend and create a social network integrated browser? I have to believe many individuals, especially university students and less techy facebook addicts, would use a browser by FB. Undoubtedly productivity would go down, but I doubt that's what Mark Z is concerned about. I am interested to hear your thoughts.