It sound legitamate. Afterall what would someone have to gain by getting you to add their friendcode? Especially seeing as they would have to of hacked into the survey database to know you did it, what the prize was and you e-mail!
"The universe has to move forward. Pain and loss, they define us as much as happiness or love. Whether it's a world, or a relationship...everything has its time. And everything ends."-Elizabeth Sladen: RIP.