I think I'm liking this. I would like it further extended to multiple identities for bookmarks and cookies since as they point out, it's too easy to get confused when they're the same for all identities. But it's a start.
Right now, I'm using Firefox for some things and Chrome under the anon style for others. I log in to things so I'm not fooling myself into thinking that I'm cloaked or anything. I just like to keep things separate.