Facebook has 2.2 billion monthly active users[1]. That's billion, with a B. HN has 3.5 million (with an M) unique visitors per month[2]. Everyone on Hacker News AND the 10 people closest to them could all drop off Facebook and it would only be about 1.5% of Facebook's traffic. Are you sure that the trends you're mentioning are happening outside your social circle? I'm not.