There's a new numerical field in user profiles called "past names" which when clicked will display a dialog listing previous usernames and when they were last used.
That's pretty snazzy. And it almost addresses an issue I brought up a long, long time ago, when the 30-day name-change restriction was put into place:
Personally, I found it much more confusing when certain users who had gone months under one name suddenly switched to new names (and, in at least one case, new gravatar images).
Rate-limiting would do nothing to prevent this, but banning name-changes outright would hamper those who picked unfortunate pseudonyms, were poorly-named by their parents, or decide to change their names out of some misguided ideas of transparency.
Just one problem: that little pop-up list is only available to moderators and the name-changing users themselves. Sure that's great for me - I have mod-privileges on all the sites now - but what about all the poor confused users caught soin my former dilemma of finding yourself in the middle of a discussion with someone you could swear used to be named something else...
Let's face it - this is already public information. If you think a user has changed their name, you can pull an old data dump, or even just bring up the Google cache of their profile and find out what it was.
Of course, some folks have important reasons to change their names, to let their former identities fade into the mists of time. It'd be insensitive to ignore these concerns.
So how about this: when you change your name, the full list of all your past names shows up on your profile for 30 days. After that, it no longer shows up (to anyone other than you and the moderators) until you change your name again. Maybe fade the link a bit to indicate this.
A month to settle into a new ID, and a month to clean up any loose ends with your old one.