This is a neat image I found on the internets. (Click it to make it larger.)
It is a clever collage that shows which conglomerates own our favorite brands. While I was familiar with soft drink brand ownership, I learned quite a bit from the snack quadrant of this image.
You'll notice that quite a few brands which compete with each other on store shelves are ultimately owned by the same corporation. My understanding is that despite this, each brand markets independently in an intense competition for market share, shelf space, etc., and the mother company ultimately benefits from all this.
This is all the result of companies buying out each other for centuries along with a relentless hunger for market share. I guess the ultimate take-away here is that it'd be really hard to boycott any of these companies, but until then, I fully plan to support them by buying their delicious products!