I always wondered if the thought processes went something like “Hey, what a GREAT idea! I’d be stupid NOT to do this!”
Obviously you don’t just get up one day and decide to open up your ass. You work up to it gradually. I assume it took a long time before the Goatse guy could do that.
And inkleberry, for all kinds of weird body modifications, check out bmezine.com. That site is not safe for work though, so look out.