Is it possible? Sure it is. We're working with computers here, sometimes they fail. Harsh reality, but it's true (note the mail/MySQL problems that some have been having).
Is it likely to happen? Not really. I'm sure that DH's systems are designed well enough that the chances of this happening are next to nothing. Kinda like winning the lottery.
As suggested by Simon, though, if your information is absolutly crucial to you, do frequent back-ups (phpmyadmin - or from shelll access if you kow how to do it) and should something nasty happen, you don't lose all of your info.