[dmm]

Here's a good example:

http://slashdot.org/story/06/11/09/1534204/slashdot-posting-...

Slashdot got over 16,777,216 comments overflowing a MySQL mediumint they were using for an index.

[daigoba66]

Same thing happened to Twitter: http://techcrunch.com/2009/06/12/all-hell-may-break-loose-on...