"Babe Ruth had only one home run. He just kept hitting it over and over again."
In response to an analysts question that Apple was limiting its opportunity in the phone market by only having one SKU (stock keeping units). If you care to listen the discussion starts around the 54:12 mark of the call.
And unless I am mistaken Apple currently has three different SKUs. 8GB black, 16GB black, and 16GB white.