Since a few dollars in opinion have been spent here, I'll pitch in a couple pennies.
I agree with Don that 110.26 is poorly worded or this thread would not exist.
I believe that
examination, adjustment, service, maintenance pretty much applies to anything an electrician would do to equipment so the wording is unnecessary.
I believe that
likely ... while energized is the overwhelming issue of applying 110.26
I believe the working space for disconnects has been applied wrongfully in the past based on usage and not this section requirement.
I believe that there is a perception that anything with a fuse or circuit breaker is
likely to require examination and service and that line side power means energized. That a disconnect without fuses or breakers
may but is not likely to require examination or service while energized.
Therefore I do not believe that unfused disconnects would require space. I do not believe receptacles require space. I feel this is true because working on them while energized would be a violation. And though checking power of a receptacle with a meter is a common practice, there are plenty of dongles (small devices) that you can plug in to test that do not expose the live parts.
And Don? I disagree that you and Mike should agree to disagree. You should both be forced to have my opinion instead.