I've just come across this quote by AOL's Bob Pittman which I discovered here. I want to share it with you because I believe it explains the power of brands very well:
In the new world of business——a world of overcapacity and sensory overload——brands matter more than ever. Why? Because brands are a form of shorthand. Customers think about what matters to them, analyze their choice, and settle on a brand.
Once they’ve done that analysis, they’re very reluctant to do it again.