(guessing) sites like hackernews are indexed primarily by recursion (few direct inbound links to specific stories). Correct. Notice that it is difficult to fin

(guessing) sites like hackernews are indexed primarily by recursion (few direct inbound links to specific stories). Correct. Notice that it is difficult to find old HN comments on Google, since after a while there are no short paths from the home page to them. In practice & all else being equal (quality, length, spamminess, speed, age, uniqueness, PR, etc), the maximum depth a page can afford to have is about 6 or 7.