I had around 75 sites in my PBN, that consisted of a Tier 1 and Tier 2.
Tier 1: Linked to money sites
Tier 2: Linked to Tier 1 sites
My tier 2 were the mega authorative sites, as I could purchase not-so-good Tier 1 domains for cheap and boost them with PR4-PR6 links.
I had about 50 domains in my Tier 1, and 30 domains in my Tier 2.
Google took out about 30 sites from my Tier 1, and 10 sites from my Tier 2, all in one batch.
According to Statpress, nobody from Google visited those sites, at least based on IP. I cannot see any consistent IP's accessing the same 40 sites to quality check them all one-by-one.
I was under the assumption that the Google Algorithm isn't capable of deindexing sites - and only Google reviewers are able to deindex (possibly food for thought??).
Why did 40% of my PBN survive? I have no idea. There's no direct link here. Google would of been able to see 100% of my network, so I have no idea why they didn't deindex the whole thing.
My money sites are completely unaffected as of yet, and still ranking at #1. I don't expect to see a drop as I've already bought dozens of new PBN sites in bulk and working on getting them ready ASAP. So the dropped sites will be replaced.
My PBN has been running strong for about 2 and a half years, so I'm glad it lasted so long without taking a hit. I like to believe I ran it to the best of my ability in terms of keeping them hidden.
For the record, I sell no links and only place links to my own sites. Each site has around 10 OBL max.
Food for thought anyway. Anyone else been hit today?
More info as requested:
All sites on a different C-Class IP minimum, spread over about 10 different hosts.
All sites either had private whois, or fake whois information with no connection.
Sites all had different themes, and different layouts. Some homepages contained links, others only the posts contained links. There was literally no key identifier between the sites.
The only identifier is the sites I linked to (my money sites). I don't see how the algorithm could have flagged all of the sites. A google reviewer must of stumbled across one, and siphoned through majority of my network.