If it becomes worn to the point of breaking it can cause permanent damage to the receiving end of the fuel pump, without replacement it is common for followers to have full holes worn though them. The worn down follower will leave your fuel pump damaged, this being the common failure point of this set up. Replacing this follower as a form of preventative maintenance can save you from spending even more money and time replacing your fuel pump or camshaft from damages done from a warn through follower.