Right now, your homepage makes no mention of us following websites, just a search box. It's also easy to miss or not understand the "The network is built on top websites on Hacker News" message in the results page, so people might not understand that it's just the default and is customizable.

Your HN text above in the post does a good job of clarifying things, but I think some more messaging is needed in the website itself to make its potential clear. (Not many people are going to bother checking "How it works" by themselves.)

I'd suggest in the homepage, below "Grasp is a search engine for your personal network of high-quality websites.", have a "create your personal network" link (that could take you to the sign up page or wherever appropriate). And in the results page for the default network, have an info box at the top mentioning that this is just the default network, and the user can customize it, along with a to the "How it works" page.