"Hello, Commander," reads a post on the game's official website. "Many of our operatives have fallen in the fight to protect Earth from the alien invasion. To honor their memory, we have provided a means to commemorate their courageous efforts. Though they are gone, they will not be forgotten."
The Facebook app is user generated from within the app and does not come from the game. You can check out the memorial wall to submit your own entry and see cards memorializing fallen heroes like Sergio Mendes, "the lone Squaddie brought along with a veteran crew." Mendes died a hero after killing four aliens, being overtaken and then "dispatched" by a friendly grenade. You can also check out the first episode Polygon's weekly video series, Cooperatives, which features XCOM: Enemy Unknown.