First of all, threads decay. Regardless of the importance of the topic. It is not as simple as 'survival of the fittest' where important threads will continue to be commented on and thus remain near the top of the pile. The need for 'sticky threads' proves this. The problem is the linear nature of threads: everyone sees the top post, and the second, but somewhere near the first page break, a thread reaches its half lifeyou know you seldom read the second page, never the fourth, so why bother commenting on a thread that's reached maturity? Not to mention how inevitably threads get hijacked and the conversation becomes about a comment that isn't remotely related to the original post. Or how all topics get stale no matter how interesting, and sometimes we need a break. Does that mean we should never discuss it again? And when someone does decide enough time's gone by, is he/she expected to click through pages of threads until the correct one from two weeks ago is found?