My wife and I share the same iTunes music library and while most of our music taste overlap, there is the wayward song or artist that she listens too that I can't stand.
Of course, I only notice that an artists or song has snuck onto my iPhone while I'm listening to my iPhone. I used to think that I could remember to remove the offending song from my iPhone the next time I synced the device,. But of course, I always forgot. I figured out a quick way to remove the offending song while on the go.