First of all thank you for this forum full of very usefull information. I am a noob in SEO. I have been reading for a couple a weeks stuff about PBN, their footprints, linkbuilding and so on... The notion of tier 1/2/3 is often mentionned and altough I couldn't get some article about it, I have understood that tier 1 directly link to your money site, tier2 link to tier 1 and so on. If you can give me some pointers to good ressources about tiers, link structure etc, I would be very gratefull. Here come my question: if google algo is smart enough to detect spammy links in tier 3, why would it be so dumb not to explore one level up, and give penalty to the whole network, I mean tier3, then tier2, then tier1 ? I feel like I am missing something here, why the "tier" structure would be a shield against google penalty ? Thanks in advance, and sorry if it's a noobish question.