URLs and "updated web sites"

I have a client that came to me with her departments' new web site. I noticed that the new site had a similar directory structure, but all the names had changed.. Every URL that anyone had bookmarked on the site would now be broken. Maintaining the site structure had not even been considered.

This should be the first consideration of a redesign. Is there a good reason for change? If not, don't change it. Your customers will thank you.