Ask HN: Why is there no bookmark notifications API in browsers?

I've often wondered this. For site/app owners how can you track how many bookmarks you've received? It's the most basic social signal since the beginning of the web yet it's still the largest black hole out there in metrics.

Simple JavaScript API to detect when user bookmarks site, while on the site. I'd love to know if my site receives bookmarks, I'm sure others would too. Why is there no API for this in HTML5?