Interesting post on the subject at Branding Management:
Think of your brand as a promise … a promise you make to your clients, prospects, employees, and even your vendors. But before you make that promise, be sure you never forget this fact. It is imperative that you are able to back it up. You cannot build a successful, long-term brand on unsupported claims and wishful thinking. History is littered with companies — big and small — that have promoted themselves or their products as something they would like to have lived up to but could not.
To separate you from your competition, your brand — your promise — has to differentiate you from others in the minds of your prospects. This is the reason you cannot use quality, integrity, or price when positioning yourself in your marketplace. So many companies claim to offer these particular characteristics that none of them stand out from the others. BMW has taken note of this. Although it is thought by many to be the best car made, the company has built its brand as “a driving machine.” It sells the experience. BMW knows that there are other high quality cars on the market, so a brand built on quality would be diluted and therefore, less profitable.