I've had a secondhand iPhone for three years, using it with my iCloud account. Just now I tried to wipe it with an iTunes restore. The first step was to disable Find My iPhone. Doing so, I received a confirmation email that the phone is now unlocked. To my surprise, upon reset, it went into activation lock mode and asked for the previous owner's login.
The phone is listed in my iCloud Settings. Should I try to track down the previous owner, or will removing it from my own iCloud Settings page free it? (But removing it will also wipe the last evidence that the phone is mine.)
Another way of looking at the question: Can a single phone be listed in several iCloud accounts?