Rookies are usually not part of the original pool, so that doesn't apply. Parker was part of the original pool in 2008, but that's because she was selected to play with the National team while she was still in college. Fowles was not part of the original pool, but she was selected to the National team as a rookie. Nneka's case should have been similar to Fowles. There are WNBA coaches that have publically stated that Nneka should have been included. The rationale is that the top young players need to be developed for the future years. These young players will also accept the role of being the understudy players that will come off the bench behind the more experienced players and they won't complain about lack of playing time, as what was suggested earlier in this thread. Typically, the older players do not make the Olympic team for a first time around, because the committee places more importance on getting the younger players some experience.
You stated that Nneka's numbers aren't nearly as good as some of those others, but Maya's aren't either. Nneka's numbers are better. I have no problem with Maya being on the team because she is part of that youth. Using her numbers as an argument would not favor her being on the team. Maya's the future, as is Nneka. The next go around, it's quite possible that Sue, DT, Catchings, Cash, Jones, Augustus, and Whelan all may be past their prime for the next Olympics. That leaves 5 returning players the next time around, which means lack of experience for the next team. Typically, they do a better job of balancing the team from very experienced players to players with little experience to players with no experience.
As for Nneka having something unique, she does. Nneka is a relentless worker with a nose for the ball. As a rookie, she's in the top 10 in the league with her overall numbers, statiscally speaking. No player from this class or even last year's class is in that group.