CNet raises an interesting problem: what happens if you die without telling anyone your passwords? It could be a real problem for your heirs:
"He did not keep a hard copy address book. I think everything was online," said [San Francisco poet William] Talcott's daughter, Julie Talcott-Fuller. "There were people he knew that I haven't been able to contact. It's been very hard."
"Yahoo (his e-mail provider) said it wouldn't give out the information due to privacy laws, but my dad is dead so I don't understand that," she said.
One solution is to use a secure password storage facility, like Bruce Schneier's Password Safe, and then put the master password in trusted escrow like a safe-deposit box or your attorney's office. Of course, you'll have to keep up with this, because you'll change your master password at least every three months, right?