I like to see the riders wearing them. Only in the discipline they won them in of course, but I like to see them.
The only exception to the "only in the discipline they won them in" rule for me though would be Will Walker, if he was still racing. He won the 2006 Australian U23 road championships, so by that rule he could only wear the bands while racing as an under 23.
I would make an exception here though because the race was combined with the elite category. Walker soloed about 15km to cross the line first, but because he was 20 at the time, and the guy who crossed second was also under 23, it was the third guy across the line who got the jersey and the right to wear the bands for open races. A bit harsh, I always thought, so I would let Walker wear the bands for open races...