Exactly this. All posts on the internet act as a selection filter; the people most likely to comment are those with strong feelings on the subject. When we read comments, we tend to think "wow, I just read 10 comments and all but one hated the UI! People must really dislike this UI". But our sample isn't random, it's heavily biased! And we develop a biased understanding of the general population -- the vast majority of whom won't have left a comment at all. Instead of thinking "9/10 people dislike this UI", it's probably closer to "9 people out of all Firefox users dislike this UI". And more exactly, it's "9 people out of all Firefox users who saw this on HackerNews dislike this UI." Actually, I wonder if you can use Bayes' theorem to get the actual population's distribution somehow...