ZOL FAQ proposes to use whole disk, therefore partitioning is not required. From the same reason, it is not neccessary to create a partition table (be it GPT or ms-dos compatible), ZFS will create it automatically.
However, it might still be useful to use a single partition, which is slightly smaller than the size of the disk. This is to allow for problems at the time of disk replacement (e.g. due to failure). Not all disk marketed as 2TB HDD are of the same size and it is not possible to replace a drive in ZFS's vdev with a smaller drive (even when smaller by a few sectors).
I was getting errors when trying to create a zpool using the whole disk without partions. These are on 4 3TB drives that once had a btrfs partiton on them. I am going to now zero out all of my drives with dd and see if I still get the error when trying to create a pool without partitions. Unfortunately this takes 12 hours. --Demizer (talk) 21:47, 13 August 2012 (UTC)