> For the love of all that is good, don't do this ...
I, too, was astounded that anybody would be recommending keeping your keys 'public' like this. By all means, keep it on a few USB sticks that are nicely secure - and have a good plan in place in case you lose one.
By all means, have a separate, passphrase-protected key for each separate device (desktop, laptop, tablet) and push them to your machines using something like chef and the 'users' and 'sudo' community cookbooks, at a minimum, and destroy the .pem after you initially set up the host.
There is a reason that Amazon only configures one user with only one key, and it's not because that's how sane people access their machine.
I, too, was astounded that anybody would be recommending keeping your keys 'public' like this. By all means, keep it on a few USB sticks that are nicely secure - and have a good plan in place in case you lose one.