Ask HN: Why so many SEO posts all of a sudden?

This morning I have observed three SEO posts in the top 15 links on Hacker News: - Black Hat SEO Case Study: How Mahalo Makes Black Look White - Some SEO Advice For Bill Gates - Strategic SEO for Startups Is this a coincidence, or can it be explained by something else, such as a sudden influx of SEO types to this forum?