I believe you need one to download apps though. for instance, I think the apps that come with the mac from the store don't reappear if you recover the OS unless you sign into the app store.
That might well be true. I only use the Mac App Store to download Xcode and update first-party software, so I'm not sure (and, at any rate, I'm signed in to an iCloud account, so I wouldn't know if that part doesn't work without one). I seem to recall non-logged-in ones having all the built-in software in the past, but it might not be true anymore.
