Look at D&T's math in the post above yours. Transaction verification can't happen at non-trivial transaction rates on general purpose CPUs with block times that short. If you want 1 minute blocks with PayPal-like transaction volumes and acceptable orphan rates you've made it so all full nodes require ASICs just for transaction verification, let alone mining.

I can see that being a requirement at some point, but not this early in the adoption curve. Maybe when we've got a "market cap" in the tens of trillions of dollars equivalent and the transaction rate is somewhere in the 100,000+/second range it would be reasonable to expect full nodes to run on specialized hardware, but by then the economy will be so well developed that there won't be any need to shorten the block time because any problems that a 600 second interval cause would have been long since solved.