Copy & Pasted partition inherits an identical UUID
Binary package hint: gparted
If you use parted to Copy & Paste a partition, then it will have an identical UUID.
While that may be the correct behaviour for pasting on a different disk, when the partition is on the *same* disk (e.g. you want to migrate /home to a separate partition without messing around with cpio/tar/cp) then it's almost certainly incorrect behaviour.
In this day and age of mounting by UUID, having multiple partitions with the same UUID is disastrous and very confusing:
* The output of "mount" is incorrect
* You have no idea which one is being mounted
* "umount" gets confused and refuses to let you unmount the correct partition
You can recreate this easily using a flash drive.
(This isn't a problem I have had personally, although I've recreated it; it was reported to me on IRC)
Tested on gutsy/amd64:
ii gparted 0.3.3-2ubuntu6.1 GNOME partition editor
ii libparted1.7-1 1.7.1-5.1ubuntu8 The GNU Parted disk partitioning shared library