I would encrypt it, store the passphrase somewhere (or tell it to your wife) and put (a link to) the file up on DMS. This way, you have nothing to lose.
A dead man's switch is interesting to me, because it is one way to (try to) work around the what-if's that can foil the best laid plans of the unimaginative deceased.
Any solution where the sensitive information is physically near me doesn't work well -- what if I die when my house burns down, and my computer and paper documents are destroyed? What if I carefully document everything, store the document encrypted offsite, and make sure my wife knows the password.. and we die together in a car crash?
There needs to be a solution that lives somewhere I don't, and doesn't rely on people I normally accompany on airplanes, in cars, in dark alleyways...
One "what-if" that is super-important to an email-based dead man's switch -- how are your email servers set up for getting email through? I.e, DKIM, RDNS... all of the tricks & protocols that Google uses (and if you don't, you'll end up in the Hotmail junk folder more often than not), processing of auto-replies like Earthlink's whitelist system, etc..
