Obvious to you. Amazing to others.
This is why it annoys me when someone posts a link to some advice on HN, a bunch of commenters are talking about how they had never thought of it before and how useful it is, and then someone has to leap in saying "This stuff is old hat.  Everyone has heard of this before.  I thought of it myself back in 1843."<p>Because everyone has to learn some time, and what is obvious to one person isn't obvious to the next one.  And anything which helps people realise something true is worth repeating from time to time.