I'd love to have an alternative to storing usernames and passwords. I wrote a web based twitter/identi.ca client mainly for my own use, but it's public and there are people using it, and I've been thinking about purging the auth data every month or so mainly because if I hadn't written it there's no way I'd just blindly hand over my password to some weirdo who happened to write a handy client for my phone. At least then the users could be assured that their authentication info will be removed at a predictable interval.