I announced the creation of a class here on HN ( https://news.ycombinator.com/item?id=5862102 -- This was a Show HN, but then it was edited for some reason; link is dead now, but it was a blog post describing the class and had a payment link), which went on to sell out in the first day, then eventually I posted on HN that I wanted to sell it ( https://news.ycombinator.com/item?id=14933206 ), and was acquired because of the post.