What exactly are the 10 instances? Did you add VPS's or just more child processes to handle connections?

If you haven't already, it's good practice to calculate how much resources one instance/thread/process of your server takes up, and then allocate as much as your server allows. (of course take into consideration shared memory/copy-on-write when calculating limits)

Do you mind sharing some details? This happens to a lot of sites so it would be interesting to know what your initial configuration was and what you scaled up to.

Happened a long time ago, but my site (http://isitup.org :P) hit the front page of Reddit: http://imgur.com/a/UUY8d

Unfortunately I seem to have lost the bandwidth stats, but the load is the cool one. And my poor VPS didn't actually crash through all that.

There are heaps of blog posts on HN, digg, reddit, slashdot etc from overly excited dudes who can't wait to show us what a one day spike then decline back to nothing looks like in Google Analytics.