It seems like it ought to be simple enough to devise some sort of password safe. The purpose of this safe would be to contain your "master password". To determine the password to the safe, you would have to combine information many of your friends know. For instance, you might leave instructions for finding the password that say something like "what was the name of John's first pet", or "what was Mary's 3rd grade teacher's name". They would be questions for which only that person or people close to them would know the answer, and something that isn't available by Googling.
Assuming you spread your questions out over a large enough group of people (so there isn't overlap, i.e. not everyone the questions are targeted at know each other) you should be able to come up with a relatively secure password mechanism. The problem is that you'd either need to tell everyone the question's you're using and instruct them not to answer those questions for someone other than you, or you'd have to deal with the possibility of a 3rd party finding your instructions and going on a scavenger hunt to find the answers to unlock the password.
But in general, I think this idea is fairly solid. One down side is you'd have to keep your instructions up to date, if one of your friends dies and they're the only person that could answer a given question then you might end up locked out.