We live in a consumer culture that is saturated with marketing. Short of going off the grid and living like the Amish, it's hard to avoid someone trying to sell you something. Because of the increased number of "screens" (computers, cell phones), kids and teens are spending lots of time away from where traditional advertising used to be - in between TV shows and clearly labeled in the pages of magazines. Brands are now integrated seamlessly into content (product placement), and online destinations are either flooded with online ads or corporate entities trying to be your friends or they are created by brands, i.e. Webkinz. Because of this new landscape, parents have to educate kids and teens to identify marketing and explain the real motivation behind a certain viral video and that the real goal of a brand's website is to ultimately get them (or you as the parent) to buy certain products.

That said, if a brand happens to create a website that offers educational opportunities, as long as you teach marketing literacy, I don't see a problem with allowing your kids to spend supervised, limited time on these sites. Evidently a few brands have created online destinations kids can actually learn something from. Stars for Kids (a market research firm) asked teachers to rank which of these branded sites could actually be useful. Here's more from their report (.pdf):

Using a National Learning Standards Checklist with over 1,000 discrete elementary school grade standards across all curriculum areas, 80 teacher/evaluators measured the potential for learning enrichment on the studied 100+ sites. They were also asked which branded websites they would use to enrich their classroom lessons. The following five sites came out on top:

1. Planet Orange
Teaches: Math, algebra, measurement, economics, geography, social studies, language arts

2. Crayola
Art, visual literacy, science, technology

3. Dole 5 A Day
Health, nutrition, math, measurement, problem solving

4. American Girl
Math, measurement, problem solving, art, visual literacy

5. Millsberry
Social studies, visual literacy, math, language arts, health and safety

Obviously these sites are also selling financial planning, crayons, fruit, dolls and cereal. But if you're clear with kids about this before they log on and point it out when you encounter commercial messages in the content, you can take advantage of an opportunity for real learning both about marketing and health, language arts, math, problem solving...