In this question, it is stated that by driving Curiosity backwards they could get more mileage out of it's wheels, as the rocker bogie puts less pressure on them that way.
Now, the obvious question is: Why didn't they mount it that way in the first place? What advantage does the current configuration give them that they designed the rover with 4 wheels on a push arm and 2 draggers instead of all the way round?
Clarification after comments.
The push vs pull configuration of the arm is independent of the local geology and the ground. An obvious failure scenario for a rover is that one of the wheel motors should die (this indeed happened to Spirit on 2006, five years before Curiosity's launch). In that case, the wheel will be pushed by rest.
If the arm is pushing the wheel, the geometry is such that if the wheel has to go up, it also has to move slightly forward; that adds a level of stress to the whole assembly. If the arm is pulling, the wheel moves backwards when going up, which actually alleviates the pressure on the whole system.
So every time the rover has to move over irregular ground the wheels on the pusher arms will sustain a slightly greater stress than on the pullers. This applies not only to the wheels but also to the arms, bearings and the whole assembly itself.
So it seems to me that by putting two wheels on pushers and four on pullers they would have saved themselves some stress on the whole assembly, the fact that they didn't hints that either my analysis is wrong or that I'm overlooking something else.