My take on why so many people think alike and any idea you have is usually thought up already; is that people get the same inputs.
We all read practically the same news, read the same top ten books, watch the same Tv. talk about the same subjects. Sure we all have different areas(Software Entrepenuers -> HN) but in reality we all have the same inputs and outputs no matter how special we feel.
I don't remember the last time I read a top-ten book, and my list of recently-read books is probably wildly different from yours, as are both from a random third person here. The Internet opens up news and alternative news dramatically -- it's not a three-channel world and hasn't been for a long time, which brings me to TV -- a lot of people here don't watch it at all. I don't watch much. "Same subjects" might be true from a big enough view -- there are only so many categories of thought to go around, but within politics, science, world events, local events, philosophy, games, sports, etc., there's a lot of territory to make up a huge variety of subjects that people talk about.
Oh, and even though I disagree with your post and recognize that it's irrelevant to the article, I voted it up because it's relevant to the topic at hand and shouldn't have been voted down to 0.
We all read practically the same news, read the same top ten books, watch the same Tv. talk about the same subjects. Sure we all have different areas(Software Entrepenuers -> HN) but in reality we all have the same inputs and outputs no matter how special we feel.