In the case of that encrypted database being open during the backup, would that not be covered by DEVONThink asking after a potential restore whether I really want to open that database? Just as if DT had crashed on me.
So I will simply click yes and problem solved?
In any case, this discussion has gone a bit beyond my original question. It seems to me so far that the answer to my questions is: No, there are no significant downsides aside from the possibility of losing the password.