Have they not heard of Amazon EC2? Google Compute Engine? Heroku? Azure?!
"Adding more servers" - what is it, the 90s? Amateurs..
We've learnt that you can never add enough servers to cope with an unpredictable and quickly-changing demand curve. That's why they invented elastic computing. They add 3 servers now, next month those 3 servers can't handle. So they add 3 more, and so on and so on.
+1 that; either that, or, in case their regulations insist they run in a closed-doors DC, then they MUST make sure that their normal trading volume is not loading any part of the system higher than 10%. 3x increase in volume should be absolutely normal and should not cause even a slightest delay.
Amateurs indeed. Bitstamp has heavily lagged as well, the only exchange operating normally was btc-e.