According to this article from CVG, FIFA 10 cover star Wayne Rooney has had to change his Xbox Live gamertag recently after people discovered it was the real Rooney. See this quote:
My gamertag used to be Wazza10 but I had to change it when too many people found out it really was me. I still play FIFA regularly online though!
I wonder what his new gamertag is… Thanks to Nanny from the forums for the heads-up!