Ditto. I signed in and realized what was happening, looked for options in settings... no dice. I tried to sign out, and then it was going to sign me out of BOTH carousel and dropbox, so I just deleted the app. I think you should at least have the option to choose whether you want to update your previous photos, if not more granular controls.

I like their concept of simple sharing of albums. I shouldn't have to sync every photo to use it, though.