What if an admin dies? Should access to the servers die with him?
Every organization I've seen has disaster recovery procedures. Just follow them. The comments I made earlier about "terminating sysadmins" pertain to terminating those who don't follow them for one reason or the other. It really isn't a computer-science-specific problem, more like general organizational management problem.
With one man shops (like bitcointalk.org) the situation is simplified. Loss of access requires disassembly of the server to reset its password protections. If there was encryption in use, those data are (most likely) irretrievably lost and the server requires reinstallation with the fresh software. The reset/reimage is not something that can be done quickly, surreptitiously or socially-engineered into the normal workflow of the customer service of the data center. I've never heard of anyone successfully performing such an attack, but I've heard of performing similar attack where the goal wasn't to steal the data but to steal the hardware.
I personally wouldn't bother thinking much about it. In all cases that I've seen/experienced the password loss was temporary, i.e. the person recalled/found the proper password after giving it some time. The true loss happened only if there wasn't anything important on the server anyways.
The real, practical danger with one-man shops is not the password loss, but grave mistakes, that corrupt the data on the server without getting noticed.