Change when no change is required

Why do some people/companies feel the need to do something, just for the sake of showing they are actually doing something. Granted this is how everyone remains employed, gets their annual budget, keeps the investors happy, etc. But sometimes there really isn't a need to make the changes that are made.

A perfect example is Facebook. The social networking site was growing by leaps and bounds and had millions and millions of members. Members were enjoying the ease of using it and were becoming actively involved in the community, creating applications, games, groups and widgets. Then they decided to change the interface for some reason. Now granted the change was not exceptionally harsh but even in my group of friends who's status' I see daily I have seen more than a few grumbles and groans. Why chance angering and alienting your members by making a change that doesn't appear necessary. Why not focus on improving the interactions among members and creating more and more cool applications to keep people interested in the site.

Another angle on this would be the stubborness of humans and how we hate when things we know are changed on us. We will adapt to it, but the majority of the population will mutter under their breath while they do.

Just makes you think the next time you are changing something.

Is there a need for this? What is the strategy behind this decision? What will our customers reaction be?