Sites built for two - Coupleware

I was chatting with kellan about the wesabe finance site and how it's pretty cool. You can load up your data and check it out, find out where you're spending money without realizing it. I've also started using Book Mooch for sharing old books i don't any longer.

The problem is that for our household books, and for finances, they are family things. I don't decide what books we want to keep, or how we're spending money along. It's a two couple thing. gaba and i do all that stuff together.

But those sites don't have a concept of couples. Two people who their own identities and logins, but who share the same data. I want there to be a coupleware design pattern. Where two users can share all of their information. But get settings like notification, identity, etc.. separately. Right now the only way to do it is to share a single login and password. That's a kludgy hack. Come on folks, you can do better than that!