People at the top of the pyramid almost always suffer from groupthink more than anyone else, because they have the fewest people both able and willing to say no to them.
I see this all the time, and it happens on HN a lot too.
Someone will post a link to their startup, and everyone will be supportive and at most suggest a few wording corrections.
I'm often tempted to post "this is shit, and here is why", but I think the supportive environment of HN is valuable. I don't know what the solution is.
What this really highlights is that entrepreneurs aren't put face to face with someone as incisive and BS-resistant as PG or Harj nearly often enough.
Maybe there's an opportunity for an Ask Your Target Market like service which specializes in reality checks for entrepreneurs.