Proof of keys? I control my own keys thank you.

Trusted third parties? Isn't that an oxymoron?

I haven't had any coins on an exchange since MtGox. Luckily that mistake only cost me 50BTC. Never again.

Closest thing I have to a trusted third party is my Trezor which I somehow got talked into using against my better judgment. Luckily I only have 5BTC on it. I stopped using it last year after having it for less than half a year.

Obviously cold ("paper" wallet) storage is much more secure. Only I have control over the keys and they're never exposed to the internet except when I sweep a wallet into Mycelium to transfer coins and that's only small amounts for short periods of time.  

This is why it's good to spread your stash between dozens or hundreds of small wallets. My biggest single wallet has a little over 30 coins in it (from pulling out what I had at Cavirtex after being Goxed) but I'm almost scared to sweep it to split it into smaller wallets because that would entail risking that many coins at once by exposing them to the internet.

I suppose I should empty my Trezor on Genesis Block Day as a way to assert ownership of my keys instead of trusting Trezor. Then again why wait until Jan. 3?