@Iluviaporos - They've actually done studies where they were scanning the brains of people who were shown logos of, say, Coke and Pepsi and the brains of the people who were shown the Coke logo would light up as though they had seen a friend.
I suspect that advertising and other means of building a brand identity tie into our biological need for a community and our loyalty to that community.
When someone becomes a rabid fan of Apple, for example, they are creating a them vs. us mentality against all other brands. It makes them feel like they belong to something bigger than themselves. And it also creates its own little insular group where everyone is backing up the party line.
I'm not saying anything against Apple, but they do tend to attract very loyal consumers. And I don't think anyone should be that loyal to a company that exists only to make money.