How do I make an automatic tail that is bone rigged?

Question

I have character that has a bone rigged tail but how do I set up the bones to automatically behave like a real tail automatically.

For example:

Answer 1

[Updated]
Simplest tail rig ever possible.
The tail has 8 bones the last bone is its tip.

In pose mode.
Adjust all influence to about .5
Add a bone constraint to the 6th bone "track to" the 8th bone.
Add a bone constraint to the 4th bone "track to" the 6th bone.
Add a bone constraint to the 2d bone "track to" the 4th bone.

Done.