I am not particularly loyal to any brands of food. We don't buy a huge amount of processed food so in most of our shopping it is irrelevant. No brand labels that I notice on the bulk bins.

I suppose I buy the same brands a lot for baked items and the few processed foods we do buy but that is in large part due to the fact that there is often only 1 brand at the co-op we go to.
Most things, the only difference for comparable items (say evaporated milk brands and canned pea brands) it is exceedingly likely that they foods come from the same manufacturer. The dog food recall that is going on highlights this- multiple brands from multiple companies all recalled for poisioning pets because the food comes from the same factory, from a company whose name you never read on the package or see ads for.
Before we swiched mostly to organics, I suppose I did prefer Cheerios to other O type cereals.

And my totally hypocritical use of diet soda- I drink diet coke, not diet store brand or diet pepsi etc.