"If you're marketing beverages which are high in sugar, high in caffeine to kids, those drinks are probably going to be replacing other things that they would drink or eat otherwise," said Geoff Ball, a pediatrics professor at the University of Alberta. "There really are some mixed messages, and not everybody is on the same page."

While Starbucks doesn't explicitly market to the youth set yet, the company has a long-standing tradition of involvement with programs and other initiatives that focus on children. For instance, Starbucks has joined with Frontier College to fund Starbucks Summer Writing Camps, which bring together youth from inner-city schools in Canada to learn about writing.

"Kids don't have a really good idea of what marketing is. They're very influential and some would argue a vulnerable population in some respects," Ball said. Ball also wonders if it is "responsible from an adult perspective to be pushing products onto kids they don't necessarily need?"