Informative post and comments, but I think it's generally a mess. Steemit should have this feature built-in, we shouldn't have to use 3rd party website.
They don't store the keys that you enter in steemconnect.
Ok, that's interesting, so where is it stored? In a cookie? I hope it's at least properly encrypted...
Edit: Maybe I was too harsh calling it a mess, we have to remember it's all build on top of blockchain.