If you read the linked article, aside from the very beginning, he uses Sleepwatcher [1] to trigger an Automator script that launches Photo Booth and does the 3...2...1 countdown.
Sorry, I should have been more clear. I was wondering if he remembered that the script would launch PhotoBooth before he opened the lid each time. I expect he'd have just grabbed his MacBook and opened the lid and then remembered that it would take a picture.
As it happens all of the time I really don't forget. And if it takes a really horrible photo I can always just click the little X and delete it so no harm.
[1] http://www.bernhard-baehr.de/
[2] http://www.apple.com/macosx/what-is-macosx/apps-and-utilitie...
[3] http://www.apple.com/macosx/what-is-macosx/apps-and-utilitie...