A commenter already mention this. Lots of companies got hit really hard from the Penguin update because of bad links pointing to them. So I'm not surprised they're being overly aggressive about this.
Speaking of the Penguin update, I'm surprised and quite disappointed it hasn't been talked about in HN. It affects a lot of consumer web startups. Anyone who has a website basically should be concerned.
Yes, and in the process also taking out innocent websites as well. This isn't an algorithm update against "bad" websites. It's an algorithm update that negatively affects websites that fit a certain pattern - and you can fit that pattern without even being shady.
For example, if someone doing negative SEO by blasting 10,000 bad, spammy links pointing to your website - the penguin update penalizes your site. Even if your site is about helping cancer patients, or feeding Africa.
Speaking of the Penguin update, I'm surprised and quite disappointed it hasn't been talked about in HN. It affects a lot of consumer web startups. Anyone who has a website basically should be concerned.