Very fun project and still working on expanding the index. The condition to get into the index is no/low bloat/tracking/spam.
Maybe it could work if you charge users a super small base fee (let's say $1/month), and charge commercial sites that want to be listed in certain verticals?
Content owners' greed is ruining the web. Build websites without any intention of monetary gain and you'll find a much better experience in the web.
Also, even when websites are built without any intention of monetization, there are still goals which the creators want to achieve. Some sites are free because they want to change public opinion or facilitate cooperation between groups of people for a common purpose. Others are made to showcase skills or for academic purposes. Lots of people are making all kinds of websites. Some want to be paid and that's fine.
Also, I wasn't thinking of a stream-of-posts type thing -- more like private, curated search but I guess having a stream makes sense too.
Either way, the question then becomes would enough people pay whatever monthly fee would keep the site viable (pay for the curation, bandwidth, etc) to prevent the people running the service from making compromises on the vision...