But in the case of the second type of owner who happens to be a dedicated rider, there's a market need going unfulfilled, and that is, cyclo-computers with more than two available wheel size settings. They just don't exist as far as I know. The multi-bike example I gave above (and honestly, from perusing the blogosphere, I don't think this is such a rare occurence) could have 4 different wheel sizes on his bikes.
Later this year, as I rebuild my beloved touring bike, I will be in a situation where I have bike with 3 different wheel sizes, and I will be forced to go to wheel reset mode on a regular basis if I want to properly accumulate mileage (and I do.) I'll bet that the desire to have a reasonably accurate cumulative mileage (coupled with the ability to learn one and only one set of controls) would be highly attractive to a growing market segment.
So here's a great opportunity, all you manufacturers of cyclocomputers (and there's probably only about three, maybe four, of you) -- give us some flexibility!