Using USB Drives for a RAID

[Hal Vaughan <hal@thresholddigital.com>]

Has anyone built a RAID out of USB drives?  I'm considering it but I'd 
rather hear from others who may have done the same thing first.  I can 
see several possible problems.  Last time I was working with USG 
devices, if I unplugged the drives and did not plug them in using the 
same order /dev/sda could become /dev/sdb, so I could see that as an 
issue, for starters.

If anyone has experience with this, I'd like to hear about it and if 
it's a good or bad idea.

Thanks!

Hal