The habit of insisting that only the right and the left have “ideologies” and that people in the center don’t is one of the absolute most frustrating elements of conventional political discussion in the United States. The fact of the matter is that “centrist” ideological taboos have been the big story of the Obama administration. That starts with the imposition of an arbitrary cap on the size of the stimulus bill, it continues to the utterly merciless and fanatical centrist opposition to the existence of any public option, to the Fed’s refusal to undertake further monetary easing, to the unwillingness to contemplate really stern measures against bailed-out banks and their executives, and on and on and on.
The idea of a “centrist” ideology is easiest to apply to the “left-right” political spectrum in the U.S., but it holds true in other areas as well (e.g. proprietary versus open). While the “correct” answer is often between two extremes, that’s not always the case. People who tend to favor shades of grey are not necessarily more reasonable, just more prone to picking shades of grey.