I'll never forget this essay, because he first delivered it as a talk at Harvard that Steve and I trained up from Virginia to attend. After Steve had lent me Masters of Doom, I was already convinced we should start a startup together, but this talk sealed the deal. I know Chris Slowe (later our first 'hire' at reddit) was in the audience that evening and I'm sure a number of other future YCers were also there with no clue of where it would lead.
Thank you, Paul Graham, for making that comment about finding investment from rich people who'd done it before (but not him). If I recall, it was feeling guilty about hearing the dejection in the room that got him thinking about starting Y Combinator.
And what a difference that decision has made in so many of our lives.