How do I erase my work location from Google Now?
Thanks to a pointer from Pam, I waded through a number of potential solutions until I found one that seems to work:

[update] Although the steps appear to work, less than 24 hours later Google Now will automatically re-add your work address - even though you've not got it listed in Google Maps.


From Google Now home screen tap your "menu" button to open the settings (for my Galaxy S3 its the far lower left button.)
Tap "Settings" and then turn Google Now to "Off."
A confirmation box appears. Check the button that says "Also turn off Location History."
Click "Turn Off."
At the next screen, click "Turn On"
Click "Yes, I'm in."
Your "home" address should show as your current GPS location.
Scroll down until you see a "magic wand" symbol in the lower right corner and tap it.
Click "Places" (it should show a #1 next to it.)
Your Home address should appear (you can tap to edit this if not correct) and "Work" should be empty.




You will have to re-enter any other personal settings but at least you can now edit your "work" location (or just leave it blank)