"The mere possibility of being interrupted deters hackers from starting hard projects. This is why they tend to work late at night, and why it's next to impossible to write great software in a cubicle (except late at night)."

From, you guessed it, Paul Graham... (Specifically, footnote #1 of chapter 6 of Hackers and Painters, aka "How to Make Wealth" http://www.paulgraham.com/wealth.html#f1n)