When doing tiered link building, on tier 1 we usually use our best content, manually spun (or automated but checked afterwards to make sure everything is readable). For tier 2 we use scraped content that's then auto spun and results in total junk content. So tier 1 provides all the link juice... and i'm not sure what exactly is tier 2 for: is it for indexing tier 1 links or for adding more juice to the tier 1 links? If it's for indexing, i understand but if it's for more juice, i don't understand how much more juice would be added by some spammy guestbook, comment or bookmark links. I've been doing tiered link building for years and this question just popped in my head right now. I mean, i know that tier 2 is important, i've noticed that when tier 2 links kick in that's when you see a rank increase, but i still don't know the exact cause of this (indexing tier 1 or more link juice).