An original thought. I do have them once in a while....
This was inspired by looking at a picture on Astronomy Picture of the Day while thinking about markets.
Capitalism is like gravity.
An appropriate amount of gravity is essential for the development of universal "life" (stars, galaxies, planets, space-time). But if gravity becomes too concentrated, and is not moderated by other forces, it destroys everything within its reach and rips the universe apart (black holes).
Capitalism held in check by social forces and governments, and applied to social interactions where it sensibly applies and is kept out of those where it doesn't apply, is healthy, productive and arguably essential to the formation and functioning of modern society. However, if capitalistic forces become too strong, and are not held in check and moderated by other social forces, they will destroy the very society they helped create.