Dick Wolf proved you could have a successful television show even if you replaced all your main characters every few seasons. No one stopped watching Law & Order when he first tried it out, and I don't know why networks are so afraid. Yes, we want to see our favorite actors, but if the story is god enough it does not really matter who is starring in the program. Well, after facing some huge contract demands from the Jersey Shore cast, everyone realized they could find five or six other people from Jersey who are just as loud and abrasive and cost a whole lot less. When the cast comes back from Italy, they will film one last season at $100K per person per episode which is more than 90% of the actors get on network television. After that, there will be no more Snooki or The Situation. They will be free to have their 15 minutes expire.
Now, the downside to all of this is that MTV will be adding another 5 or 6 people to the list of people who do not deserve to become famous or earn millions of dollars.