Psnathome.com states:
"Yesterday, we received this nice letter from Jonathan Britton, who has probably also sent to Sony, or Sony saw the letter on our site, or various others, but Sony heard the complaint and said "here you go, want cookies with that?". The letter complained about how Sony treats other regions differently on the PlayStation Store, in this case, Europe was the one taking the beating. Sony has recently pulled up the release for the CoD4 variety map pack for Europe, creating a simultaneous worldwide release date for Thursday, April 24th. As a result of this, Infinity Ward has brought Double XP Weekend earlier than expected, because originally they were going to wait until Europe got their Map Pack, Double XP Weekend will begin at 12:01am GMT on Friday and it will finish at 11:59pm PDT on Sunday. This gives the players 8 more hours of Double XP Weekend. As another special treat "Play with Infinity Ward" day is now Friday April 25th and the developers will be playing with the users between the hours of 11am and 2pm PDT as well as between 5pm and 8pm PDT."