I don't think leaving a copy of all your passwords with your Will information properly deals with password release for relatives and significant others because we all need to change our passwords too frequently for that to be effective. Another solution is required such as having a master password file which is updated each time we change our passwords and create a new account for whatever. But then where to leave that is an issue of its own.
Leaving instructions in one's Will as to the distribution of digital property makes sense as part of the divvying out of the proceeds, but will of course only work if the various passwords are known. And bugger copyright is my view on that. The person's dead and their property ought to be distributed to the living. (Yeah, I know the flak will fly because I stated the bleeding obvious!)
But the thing that gets me is the notion of continuing to send messages to people once you're d e a d .... not my cup of tea to either send any messages nor to want to receive any!
So books, paper and ebooks should be distributed without qualm as well.
Edit
And imagine Twitter messages being sent out from the d e a d ... will they be prefaced by 'this person is dead and here's what they thought before they died'.