Looking back over the proposal guidelines, I realized I probably should have spent some time discussing the idea here on fw-auth first; but, since I'd already written most of the content for my blog, I figured it'd be easy enough to post it to the wiki.
The basic problem I'm trying to solve with this adapter is that, when designing applications that allow users to authenticate in a variety of ways (against a table, via openid, etc.), I've often found myself throwing a whole lot of repetitive logic into my controller classes. I won't go into more detail here since I've already written it in the proposal, but if this interests you, please take a look and add your comments!
I'm not totally sure yet of the naming conventions, especially for the strategy interface…that's one thing I know will need discussing.