The New York Times has an article by litigating attorney Richard S. Busch, by Beb Sisario, link here. The attorney says that musicians don't like to sue record companies because they fear blackballing.
Update: March 19
Ars Technica reports (Megan Guess) that the Gaye family has asked the judge to enjoin sales or distribution of the infringing "Blurred Lines" until royalty payments are made, link here, Also, the original work was created before a change in copyright law in 1977.
Update: March 21
Here is a New York Times review (by Anthony Tommasini) of a concert by David Kaplan on adaptations from Schumann, comparing the classical world to popular in the discussion, as to how copyright is viewed. I'll try to find more details on this later, as I was not in NYC to attend this.