Following is one item from a big list of ranking factors (15 Minute SEO List - Learn how to SEO) -------- Begin Quote ----------- #33: Cross-linking Cross-linking occurs when site A links to site B, site B links to site C and site C links back to site A. This is the simplest example but more complex schemes are possible. Cross-linking looks like disguised reciprocal link trading and is penalized. -------------------- End quote ------------ Two scenarios I need some experts share with me: Case 1: If i had a site Main.com that SELLS products A, B and C. Now I create blogs that TALKS about products and industry of A (B and resp. C). Now if I want to link back from Blog A to Main.com/A and same with B and C, is it harmful or helpful for my rankings? Case 2: 3-way link exchange with good bloggers, but topically relevant, using site-wide links and blog post links. My Blogs A, B and C links out to domain OTHER.com. Other.com links back to my Main.com. Is it harmful or helpful for my rankings? What if a company has many subsidiaries for each niche and just link from one two some others? This cannot be a reason to get penalized isnt it? Thanks everyone.
It could be harmful in the sense that you're creating a closed loop. Whenever you're cross-linking, you should randomize it so that no pattern is created. Also, never close the structure.