North Carolina's the most likely Romney state to flip, but it is historically unlikely since it requires the Democratic nominee to outperform Obama in 2012.
North Carolina is experiencing the same similar demographic trends to those of those of Virginia. The urban areas (Research Triangle, Charlotte, etc.) is gaining population while the rural parts of the state is losing population.
Furthermore, after the Republicans have taken over the state government for the first time in 130 years, they have alienate the urban dweller by pushing through far-right wing agenda.