Commercial bakers only grease and flour the bottom of their cake pans, not the sides. This is because as the cake rises it supports itself on the sides of the pans so that you don't get a cake sinking or cracking in the centre. Of course with most sponge, angel food or chiffon cakes, you do not grease the pans as the grease effects the ability of the cake to rise since much of the rising power is provided by the eggs.
We tend to grease and flour or spray, the whole pan, maily to avoid having indentations in character cakes stick or to avoid scratching our pans or to avoid cake crumbing on the sides of our cakes.
Interestingly, I happened across this information on the Betty Crocker site. I know a lot of folks use Betty Crocker mixes and this might explain any issues with sticking or breaking some folks have had.
A correctly prepared cake pan keeps the cake from sticking. For Betty's SuperMoist® cake mixes, generously grease the bottom only of pans (or lightly spray bottom with cooking spray). Use about 1 tablespoon shortening per round cake pan. When making most scratch cakes, grease the side and bottom of the pans and dust each with about 1 tablespoon flour, tapping out excess (check your recipe).
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Hugs Squirrelly Cakes

Thanks for the info Squirrelly!!!!