There's nothing wrong with celebrities entering public service, but voters should reward fame that has some kind of merit related to the office.
We have a responsibility to strike a balance between our belief in democracy -- the thought that we could all be capable of making legislative decisions -- with our belief in a republic -- that it makes sense to delegate some of our decisions to other people, who will then specialize in the process of making those decisions.
Plenty of people have become politicians because they were well-known -- Ulysses S Grant and Ronald Reagan are both good examples. But they also established themselves (Grant as a general; Reagan as a political spokesperson) and their credentials as decision-makers before entering office.
Even John McCain became "famous" in a sense before entering office -- but he became well-known for an act of great courage and character. Character is best taught by example. As a nation, we should be grateful that we have @SenJohnMcCain to emulate. May he recover speedily.