Very high memory and CPU usage by the OS X Dock

If you are using Parallels Desktop 6, this article may apply :
Dock using 100% CPU after OS X 10.6.8 update for Parallels 6 users.
The details can be found in this Parallels KB article:
Mac Dock consuming 100% of CPU core after upgrade to Mac OS X 10.6.8.

Adobe Updater in the dock is also cited as a possible cause.

To completely reset the dock back to the original factory settings, remove the files "com.apple.Dock.plist" and "com.apple.Dock.db" from your /username/Library/Preferences/ folder, and then log out and back in again. Be sure to write down what you have in the Dock, so you can set it up again just as you had it.

This can also occur with VMware Fusion 4.1.1. If I quit VMware, the Dock process returns to normal CPU usage within a few seconds.

Another cause for Dock to consume >2GB real memory...

I had selected a set of photos to cycle as my desktop background. Some fo the images were rather large TIF images. This caused Dock to consume extremely large amounts of memory and CPU. Since the problem depended on image, it would seem to come and go and was therefore, hard to tie down.

Reverting to a single, normal sized JPG solved the problem completely.