In the process of recovering, I detected the need to refer to my boot partition in a location independent way. Because my Dell PowerEdge 2950 tends to insert or delete USB partitions and devices "whenever it feels like it", which causes my boot disk to be /dev/sdb1 or /dev/sdc1 or /dev/emcpowere1, I want to be able to identify it no matter what it is physically called. That's were boot labels come in handy.
See the Linux Partition HOWTO on the why and the how.
(Note: actually the server inserts/deletes USB device when you add/remove the nousbstorage from the linux kernel boot parameters.