From the article:
The problem, according to University of Minnesota Law School professor William McGeveran, is that a 104-year-old New York law prohibits advertisers from using photos, drawings or other likenesses of people without their written permission. Courts in other states as well have held that people can sue when photos or drawings of them are used in ads without their consent.
A commenter on the blog, Gerard McLean from Rivershark, Inc. also had a good point:
Brands should probably be more concerned about which naked rear-end or other body part is going to appear next to their ad rather than users’ being concerned about their likeness being used without permission. . .