Minor distracting nitpick: the post title is misleading. I thought PG was the one who said "No filter." I realize the title has no quotes, but missing quotes seems like a smaller mistake than requiring the reader to decipher what it's supposed to mean ("PG has no filter against speaking his mind, which led him to saying the meanest thing he ever said to a startup").

Better title: "Paul Graham dares to criticize, and why you should to." Or just drop the "No filter:".

Also, for the first half of the article, I thought "no filter" referred to the founders who switched focus on a whim, ie "no filter against other alluring ideas."