Here is an interview about the Gamer Card between Xbox.com and Michal Bortnik, the product manager:
Xbox.com: With Xbox Liveâ„¢, we have the Gamertag. What was the thinking behind expanding that to a gamer card?
Michal Bortnik, product manager: The starting point is that we saw a ton of evidence that people love to express themselvesâ€”they want people to know about their political views, where they’re from, their clan affiliation, even how they feel about their mom. With gamer cards, we can piggyback people’s willingness to share this information with the ability to make better matches through the Xbox Live service.
Check out the full interview in our forums [here].