Barriers to Entry
Remix of http://Wikipedia.org/wiki/Barriers_to_entry :
Competition approaches perfection as barriers to entry approach zero.
But, since Profit approaches zero as Competition approaches perfection, and since for-profit businesses measure their success according to the profit they extract, some barriers to entry must remain for Capitalism to continue.
These hindrances can also be thought of as a sort of http://en.wikipedia.org/wiki/Price_support.