Game Design - Why Change When It Works?

Today I am going to focus on a general issue which affects both Mafia Wars and Mob Wars players. That subject is Game Design.

Why is it some designers keep changing the design of their games? They have millions of active players who ENJOYED their games as they were - and yet they begin changing the whole appearance of their games?

It has long ago been established that people are annoyed by the changes made to their Facebook profiles. Recently, the so-called Timeline has been a major issue with many Facebook users. You can't go back once you have activated your Timeline.

I would agree changes are good when you fix bugs in your system.

I would also agree changes are good when you increase the speed of your applications.

But when you just make changes for the change itself - that really annoys me.

What is your stand on this?

Thanks beforehand for your feedback