I recently saw Stu Allen and Mars Hotel, and the bass player rotated between four basses each set. Each one sounded great for the chosen song.
Have to add: I'd wager that this guy would have sounded great all night long if he'd stuck to the same bass.
Obviously that would not have been feasible if he used different tunings for certain songs, or went from 4-string to 5-string, fretted to fretless. But I wouldn't understand switching between, say, four-string fretteds all tuned the same, just because each had a different tone. I've known guitarists who have grouped setlists because they had to have Strat for these songs, Les Paul for those songs... maybe their guitarist buddies would notice the difference, but most people wouldn't care if a Les Paul was used for Stevie Ray Vaughan covers.