Intellectual property is in fact an area where ambitious lawyers could make tons of money by exchanging common sense with zealousness. On the other hand, intellectual property is a very important concept in our copy-paste generation.
I see two moral issues. If a band plays a tune, does the composers name even get mentioned? I would venture to say, many of those who don't pay royalties never thought about that either. I feel that we are OBLIGATED to give credit where it is due and as far as a combo paying royalties/securing permission, that will ALWAYS be best effort. A gig with 50 "approved" tunes and you miss one encore is not the issue.
We do not need to split hairs. There is no gray area. Doing the right thing is often easier than the excuse makers are willing to accept. Civilization needs some new skills for our new age.