I think it would be nice to see the mileage/odometer in a vehicle's profile. That way, when I'm comparing my mpg to another vehicle, I can compare apples to apples. A Pinto with 3000 miles would get better MPG than a Pinto with 100,000 miles on it.
Also, if the mileage is shown, I could add more precise notes. For example: oil changes, repairs, etc.
Unfortunately in my experience mileage has little effect on economy it's actually engine care. When driving in a group/convoy, ie same driving conditions, you often find that the most economical cars range from almost new to well over 100'000 miles on the clock. Talk to the owners however & most of the big mpg cars are home serviced.
I can say that my Tahoe kept getting the same mileage as new in 2007 as it is now with 63,000 miles on it. The improvement in mileage gas been due to a change in my driving habits and not maintenance related.
What would it hurt to have the odo number show? One way to benefit from the data displayed here is to size up cars we don't now drive but might in the future. Seeing what kind of longevity a model can achieve could be interesting, especially if owners of high mileage cars provided background (e.g. "never had a wrench on the engine").