Not really. There are some brands I tend to be more attracted to for whatever reason, but I have no problem buying another if it's not available or there is a better deal on an equally good brand. I do pay attention to quality, especially with food... generic/Wal-Mart brand food will never go in my mouth because it's full of all sorts of bullshit. I try to buy organically-produced things because it's better for the Earth and also for me. I buy good quality paper towels and toilet paper because if you buy the cheapest stuff it barely works, so what's the point?
But no, I don't have a blind loyalty to any brands. Several people at my work are blindly loyal to Coca-Cola, to the point where they harass you (half-jokingly) if you drink Pepsi. I don't drink soda because it makes me feel like I'm poisoning myself, but I always found that weird... why would you care about what someone else used? Is Coca-Cola the mother of your children? Chances are, it's not. So why do you act like someone is committing a sin against you if they don't use your preferred brand?
It's consumerism at its worst working exactly as intended. Don't be a pawn!
