Oh my.......
The idea appears to be a bit of a viral marketing campaign, and players who appear as walking advertisements will receive, "compensation as payment for interacting with other avatars." Exactly what this compensation would be has yet to be revealed, though it could include real-world currency or Xbox Live items like "virtual food to keep a virtual pet, such as a virtual dog... alive and functioning."
On the other side of the interaction, players could receive compensation for dealing with the walking advertisements; one example explains that you could be asked by an "advertar" about whatever product it happens to be promoting. If you get the question right, you could win a prize, but if you get it wrong you might have to sit through a "brand-accurate message" to continue on in the quiz.
The question is what sort of framework would have to be built around these premade avatars? Would you be able to put on your Chester Cheetah avatar to compete in 1 vs. 100 and thus advertise for cheesy snacks? Play videos as Bumble Bee from Transformers in order to hype the DVD release of Transformers 2? This could just be a concept the company is kicking around, and we'll never see any implementation of it, but the idea of avatars turning into little more than advertising vehicles isn't the most pleasant to contemplate.
http://arstechnica.com/gaming/news/2009/07/advertars-coming-to-the-xbox-360.ars
What kind of payment are they planning? Probably points for being a walking-talking advertaisment.