I agree. Same phone can have different cases. But I doubt the watch will have case as an accessory. It'll be really weird to run into friends wearing the same style of watch but maybe different colors. "hey, we're wearing the matching watch today! and tomorrow, and the day after tomorrow, and ..."
Privacy? Data mining? for what? Why people still use their real data when dealing with Google? Just get the free stuff and feed Google with ton of fake info. Alternate identity is the way to internet security.