Maybe Pair Programming should be renamed continuous review?
Unit Tests are my reviewer. If the code works according to the unit tests then why is continuous review necessary?
Who wrote those unit tests? If it was you, how can you be sure that the unit tests cover all bases? A continuous human reviewer can catch issues like that, and can also make the development process much faster by suggesting improvements that cut down on development time or potential bug count. -- Brent Newhall