Same IP(s) or same location? Spoofing the location would be fairly trivial.
Same geolocation.
If someone knew Muhammed Zakir's previous location and knew that this issue would come up in advance, they could use a proxy located in the right area. But it's rather unlikely.
@theymos: TomatoCage's UID appears to have been hacked, when challenged to provide a signed message, they went offline.