Thought I will share this with you guys and maybe we can see more tests done on Penguin. I have two very similar sites in 2 different niches. They both use CTR theme. The articles are not particularly high quality but ok. I bought them on BHW. There are no outbound links on either of them. Here is how they look. The reason I shared them is this: Site1 - Penguined Site2 - No problem You can clearly see the first one was killed on the 24th. What are the differences between the two sites? The Penalized one Has 15 pages. Not all pages have links, there is one page that has 2k links, another has only 10. I bought about 60 high PR private blog posts about 6 months ago. It had a 10k wiki blast to one inner page. Anchor text is not diverse, very concentrated. Has one adsense unit at the bottom of the page. Has SEO plugin installed (meta keywords, descriptions). The Not Penalized One Has 6 pages. Every inner page has about the same number of links, homepage has a lot more (more on that later). No High PR networks at all. No wiki links. Anchor text is incredibly diverse. There was a service on BHW called something like spam gone wild, it is closed now. This site got a review copy for that service. Basically they are xrumer links but with hundreds of different anchors, and the content is different on all of them. I don't mean spun, but actully different. Has no adsense but 2 banner ads. Doesnt have SEO plugin installed (meta keywords, descriptions). My Conclusions Link quality is bullshit. The xrumer links are doing well after Penguin, given that anchor diversity is there, not sure how important the unique content is. Link velocity is bullshit. The xrumer links were built in a short timeframe. Link velocity may be important for the high PR links. Lots of high PR links popping up at the same time -> high PR blog network flag. Wiki links may not be good, but maybe its because the content is not 100% unique, Google sees lots of links with very similar content ->spammer flag. Google has seriously improved in detecting similar stuff lately. Maybe that is the real problem with all web 2.0 links? Adsense may be bad, but I doubt it is really important. Having no SEO meta tags may be beneficial? Thoughts?