Look at Condi:
Pros:
* Foreign policy experience
* Well-known
* Minority
* Woman
* Highly qualified and vetted
* Not a politician
Cons:
* Links to Bush administration - while I think it'll be irrelevant in most circumstances, being the SOS and the NSA could lead to scandals on Iraq.
* Pro-choice
* Not a politician
* Black woman - though the states where this matters probably will vote Romney anyway.
Major con: Useless, bordering on detrimental, for any campaign wanting to focus on the economy as an issue. Picking someone who's background is entirely foriegn policy oriented when the economy strains to recover would strike voters as tone deaf.