The password-generating program that I created, Oplop, has now hit version 0.3. The biggest change since the last version is that the whole idea of having various restriction filters placed on your eventual password is now gone. From practical experience it turned out that most sites are happy with what Oplop generates, otherwise sometimes there is demand for making sure there is a digit.
So now a digit is always included in any generated password. Simplifies the UI immensely. Now all one needs to do is input a label and a password to get their generated label password back; no more checkboxes!
And thanks to the power of App Engine, Oplop is online. I kept needing passwords at work and since I have not gotten around to writing an iPhone or Nokia S60 app, I decided I needed something. Well, since I am interning with the App Engine team and I already had Oplop implemented in Python, I figured I would just do an App engine application where I skip using Django and just do a bare-metal web app.
But I would like to harness the ability to store info on a per-user level for this web app. The thing holding me up is deciding how much to store. If I store labels along with any caveats for the label password for that label, then I don't have to think about having that stuff written down anywhere. Plus I could have completion suggestions for someone who is logged in. And if there is a way for someone to be logged into their Google account from an application then the label completion could extend to even application implementations of Oplop.
The security implication, though, is that if someone gets a hold of someone's label list, will that provide too much information? Chances are you could figure out where someone had an account from the label name (e.g. it's obvious what account the "amazon.com" label is for), but the labels are worthless without the master password. But if you got a hold of the master password, your accounts could all be compromised (still requires knowing the username for each account).
If I store just a list of sites where one has labels along with any password caveats for the site, then I could have a bookmarklet that tells you what the caveat is. You then still have to remember your label for the site, but at least that bit of information would not be available to anyone who manages to get a hold of your account information. But it does guarantee people will know where you have an account.
Storing both the label and corresponding site for the label gives you the perks of both, but with the combined drawbacks. I have not decided if any of these potential security issues are worth the benefits they bring at the moment.