Common bottlenecks of software

Here are two good articles for listing common bottlenecks of our software.

http://highscalability.com/blog/2012/5/16/big-list-of-20-common-bottlenecks.html

http://highscalability.com/blog/2012/2/27/zen-and-the-art-of-scaling-a-koan-and-epigram-approach.html