also if you do choose to keep a sizable balance on Mt. Gox for convenience &/or trading then as well as their Yubikey being essential, I would recommend the email address associated with it to be something like a gmail one with 2FA (can be just SMS to a non smart phone) & the passwords to both Mt. Gox & gmail to be stored & accessed with
www.lastpass.com premium service that uses another Yubikey, you can also generate good different random passwords on Lasspass - say 20 characters with a-z, CAPS, 0-9 & specials eg: 2IyR0^3Zv%#p#Nworb01*RC
+1
I forgot to add the part about the 2FA email, because it helps prevent password resets. Thats why I moved 95% of my email accounts to gmail/google apps.
Also you have to remember that MtGox handles 85% of bitcoin sales, and they almost give you Yubikeys for free if you have any volume.
I would say the chances of breaking 1 2FA is very low under 1% but breaking 2 different 2FA is Very very low.
That would leave only Exchange hacks, if an exchange hack happened to MtGox and affected under 5-10% of accounts, I think they could absorb the Cost to repay customers.
I think MtGox is almost to a point of being too big to fail because they control so much of the bitcoin sales.
But there is always the chance of a Zero Day exploit that could cause losses on MtGox.
But I think the only Safe Bitcoin Wallet at home, is an Air Gapped System.
Did you see that hack last week on a linux based system, someone was able to remote into 2 of his systems and find an unecrypted wallet backup.
I used to use VMware to setup each wallet on its own VM OS. But this route wasn't secure against key-logging.