From the Motorola Xoom support forum manager Matt.
Q: Does the XOOM have the eFuse or similar locking mechanism similar to the DroidX or is it more open like the original Droid.
A: The XOOM will have an unlockable/relockable bootloader that will enable developers to access hardware for development.
XDA has a good writeup on the difference between encrypted bootloaders and locked bootloaders. A locked bootloader, presumably can be cracked and hacked - an encrypted bootloader would mean you're S.O.L. for custom ROM's on the Xoom.
Some people had been waiting on that detail to make a final decision on the device...