Probably because he's about to sign a deal with HH Gregg to release a single on the new Maytag wall oven and the contract has a "no hyphen" clause, Jay-Z wants to be called just Jay Z from now on or something. I understand because names are important. Like, if I ever get called picked for jury duty, I'll only answer to Juror B-Real and hope I'm on an insanity trial. Spin reports:
The rapper formerly known as Jay-Z has been known to stylize his name as Jay Z for some time. Now word has trickled down through the powers-that-be that Jay Z is what we're all supposed to be calling him for the foreseeable future. Billboard editor Joe Levy reported the name change last night on Twitter, citing label sources. And Billboard has now adopted that punctuation (or lack thereof) in its articles.
So, there you go. It's just Jay Z now. You can still stay "Jay-Z" like you've always been doing, just remember that the hyphen is now silent.