Yes, Mark Zuckerberg in on Google+ (and no, he hasn't posted yet...)
And this post confirms that it is indeed the real Mark Zuckerberg trying out Google+, Facebook's new competitor, and not a fake account.

BBC News are reporting that two UK ISPs, BT and TalkTalk are seeking a judicial review of the Digital Economy Act which was rushed into law without any substantial debate in the dying days of the Labour government. Poorly-drafted and many believe unworkable, the Digital Economy Act was widely opposed by campaigners for digital rights such as Open Rights Group.
Transcript, interview, bios and more at kateray.net