Amph, 1Referee — If some trustees turn against you, the others will still protect your funds. For example, an encoded passphrase can be split between mom, dad, wife, best friend. Even if dad, wife and best friend conspire against you, mom will still hold defense (by not giving them her part of the passphrase) // I've added this to FAQ section in initial post

Raimonn, RustyNomad — You can send copies of the same piece to multiple trustees using a "split" technique:

• Split the passphrase in 2 pieces
• Send the 1st piece to mom and wife
• Send the 2nd piece to dad and best friend

Even if best friend loses his piece, dad will still have his own copy. // Added this to FAQ also

Everybody — useful suggestions, thanks! What are the other problems you can think of?