It is not just about a DJ infringing copyright, because it is easy and widespread SL could be shut down the same way a bittorrent search engine can be shut down, because it harbors said copyright infringers.
Currently, Copyright Law gives a lot of power to the industries that create the copyrighted material. Protect IP gives them not only an insane amount of power, but involves the government blocking websites by DNS, redirecting the URL to a Department of Justice takedown notice page, potentially damaging the core of the internet and also leaving the copyright infringer all but hanging on a tree limb with a noose on his or her neck, just because they linked a copyrighted song on their silly little stupid "Hi world I exist!" web site.
See: Youtube Takedown Policy, which has often removed videos for "copyright violations" and suspended entire user accounts because a search bot found a match on a song playing on someone's CD player in the background at a party and flagged the video. Unfortunately for people who get hit with Protect IP, it also gives the power to lock out your bank accounts and cancel your internet service in addition, leaving you without any financial standing to go to court and win a case. That's the kind of power that will be granted to the industry and government if Protect IP passes.
That said, Linden Realms is an interesting idea, and while I can say a lot of these features are used on the dark side of SL with additional software, some features are quite useful. User teleporting for one, would work great with the Stargate Network. No more clicking to get a map location, just walk thru the portal.