Epic took more than 20 suggestions for experience bonuses in a Valentine's event and Cliff Bleszinski and Rod Fergusson chose three. Epic's Valentine's Day "date" with Gears of War 2 will run between February 8 and February 14.
For at least three days in that span (and maybe the whole week; they haven't decided yet), Gears of War 2 will offer the following XP bonuses:
• Revives are double points in all game types
• Wingman is double normal XP (4x XP)
• Horde is double XP
I'd advise checking back at the Epic forum thread for final details on when it starts and ends, but it sounds like it'll be quite the romantic experience.