Link back to home

Amazon has a treatment of its logo that I haven’t seen before. When you roll over the logo, it indicates that it  links back to home:

Normal state


Rollover state

This would seem to be helpful, but I wonder if practically it really is. We’ve found in testing that while some users understand a site logo typically navigates back to home, many users don’t make this association (and therefore never think of clicking or rolling their mouse over the logo). So, I suspect this design approach is helpful only as additional feedback for users who are inclined to click the logo to begin with.