Rather than pay someone else to rent their user-tracking advertising system, YC built a platform where their target audience comes to them--sometimes compulsively. The influencers and evangelists among us can then multiply awareness to different audiences on their own platforms.

Whenever they want to advertise a YC business, they can just pin a story to the front page for a few hours. It's smart, subtle, seamlessly non-intrusive, and one of the better advertising experiences (relative to other ad-delivery systems), in my opinion.

If you haven't noticed, you need to tune your detector a bit closer to the noise floor.