Marketers invented the idea of things being an extension of the self, not the things.

I'm ready to propose an experiment to prove this wrong.

Let us both surround ourselves with different things. For example, let me have everything pink and fluffy, and you - everything official and strict (unless it's already your style, in which case we'll change it). Let us have a year among these things, wearing them every day and having them on our working desks and so forth. Twice - before and after the year - let us take personality tests to see how much it affects us. I'm willing to make a bet of... I don't know, three digitally-distributed video games on that we're going to be different after the year - exactly because those things were in our lives.

My point is - they didn't invent it, but, rather, use it to their benefit - which, no doubt, works great. It doesn't substract from that we came to express ourselves through the things we own. It's appealing to think that we can be independent of the society or the culture we're in, and - maybe we can, alienating ourselves in the process - but we can't stand independent of the idea of ourselves. I'm willing to bet that you won't buy items of clothing that you don't to see yourself wearing everyday because they have one more pocket - which is to say, I don't believe you're going to exchange small increase in utility for the appealing style, most of the time, which is completely fine.