PBNs are the soup de jour at the moment, with every man and his dog and (his dogs brother) building a PBN and buying expired domains like they're going out of fashion...they're the talk of this fine forum therefore it's logical to assume that they are the talk of the team at Google tasked with fighting black hat SEO, many of whom logically hang out here. They know what we know. There's been a lot of talk lately about PBNs getting de-indexed with an ever increasing frequency. We all see the rules of building an undetectable PBN touted here often enough and there's plenty of good advice on how to avoid footprints e.g different hosting accounts, faking whois etc One thing that I don't see mentioned often and probably the one thing that I would use against blackhatters building PBNs is their link pattern. Google inevitably knows which sites link to others. It seems it would be almost trivial to query their database and find out which websites link to the same websites. Lazy/new/public/oblivious PBN builders may use their entire network of PBNs to link to all of their money sites. With an algorithm that scans sites and determines that the sites linking to it have a link similarity of >5 (it links to 5 identical sites - 5 is an arbitrary number here), this could easily raise a huge red flag for further inspections, via whois or manually. This is another flag for public blog networks too, say I have a network of 10 sites (small) and 20 people pay me to put links there, it's inevitable that the outward link profiles of these sites start to look the same. Now I don't know what the safe threshold is for a similar link profile and sure perfectly legitimate sites may occasionally, although I would imagine quite rarely beyond a certain number, have links to the same sites but maybe like anchor text diversity, links to other sites dilute down this similarity but this may be purely speculation. The endpoint of all this speculation for me is not re-using PBN sites. While I'm not using 1 site to 1 PBN network as I've seen others mention, I'm certainly not overlapping on a regular basis. If I link one site to two money sites, I make sure that no other site on my PBN contains those same two links. Just something to bear in mind which seems too logical to ignore.