Each individual meme or video might not be important, but then I don't think future historians are going to spend much time studying individual artifacts in det

Each individual meme or video might not be important, but then I don't think future historians are going to spend much time studying individual artifacts in detail in the same way that current historians do. We live in the age of big data and I think future historians will be focused on aggregating and automatically analysing that data. They probably won't be reading your comment or mine but they might analyse large sets of HN comments with a view to drawing conclusions about how particular demographics act, think and feel today. And if large swathes of those comments are lost the conclusions will be skewed, particularly if the loss is not random. Our society is characterised by the constant generation and exchange of massive amounts of information. It's one of the things that sets us apart from previous generations. Preserving only a small subset of that data that we deem worthy or important will not allow future generations to fully understand today's society.