Re: Who would validate transactions if all miners shut down?
Please, spare me, dont give me answers like "it will never happen" 
This is like asking who would use the internet if all the computers where off. It's a nonsensical question. If all miners shut down, there is no bitcoin network to send transactions on, and no one to receive the transition.
If you mean just me and my buddy who is receiving the transaction are the only two nodes on the network then those will also be the only two nodes mining, and you've just undone your all miners are shut down premise.
Its not like you say. Many people can run bitcoin qt and still there could be no miners. So, before come and try to answer what wasn't asked, at least make more than one synaptic connexion.
Thanks for all the responses. It helped me to understand about the bitcoin network.