Ask HN: How does Clearbit Reveal know who I am?

When I visit https://clearbit.com/reveal there is a screenshot of a web page. I've visited the page a few times from my home internet connection, and the image has been either:

A) My personal blog (on my own domain)

B) My company's web site

It's pretty impressive (or creepy, depending on your viewpoint) that they can map my IP address to a company and/or individual identity.

I'm curious about how they do it. I have some ideas, but nothing that would explain it working so well. Maybe I entered my email address on a form on a site that shares data with Clearbit, but wouldn't my IP address change often enough that this wouldn't be useful for more than a couple of days?

Anyone else have any ideas?