I do agree with the warning.
I was playing with the commands, did not back up, and ended up deleting all trace, all posts, and all pm's made by our top poster :-( and who knows what else :-)
Backing up and restoring is not very easy either.
I had a back up at the server (have to hard disks, the second for backup every 12 hours) but it was of no use... before I could get in touch with my isp, before they answered, before i confirmed, and so on... it may take a couple of days...
Could have been worst :-)