This relates to the ebay penalty. I think one of SEland's founders actually left to take a job at Google as an evangelist. You can probably search for "ebay seo penalty" and find more references. Other notable penalties that were well documented include RapGenius and GV backed Thumbtack and Nest, which quickly had their penalties reversed if I recall correctly.

https://seobook.com/blog is the only place I follow any more, since it is more critical of the digital marketing ecosystem. There are so many snake oil salespeople and clueless marketers, so this is a refreshing commentary.

https://seroundtable.com is good for rumors and breaking news.

https://www.seobythesea.com/ a more technical blog that frequently examines Google's patents.