Choosing doFollow or noFollow

I've read a post or two in the past about link protocol in terms of black hat techniques. However, they were often heavy on the technical  side and honestly I found it confusing. I understood enough to avoid scam/spam kind of linkings - the I'll link to you if you link to me kind of thing. But the other day I was on someone's blog and they linked to Google's policy of nofollow links.

I had heard of this term and whenever I embed a link I see the option, but honestly I wasn't really sure if/when to choose nofollow. However, I was a bit troubled that I was running afoul of the policy based on these two statements:

• Buying or selling links that pass PageRank. This includes exchanging money for links, or posts that contain links; exchanging goods or services for links; or sending someone a “free” product in exchange for them writing about it and including a link
• Using automated programs or services to create links to your site

I knew the buying/selling was a no-no, but it was the "sending someone a 'free' product" that gave me pause. As a book blogger, I often receive a free book to review, which then I write about and occasionally provide a link to the author. I always include a buy link to the book. 

In my blogging group we discussed this topic a little and Melissa of Keeping Up with the Rheinlander's helped me to better understand when to mark a link as nofollow.

1. When a product I've gotten free is involved and I'm linking to the product or author
2. Links that I receive possible payment from - affiliate links
3. Any links that were placed for payment - Book Blasts and sponsored giveaway posts

So, I now I think my new posts are in compliance with the first point. But I still have a question about the second point. I've signed up for my blog to be included in Zemanta's database. When other bloggers post on topics that are related to topics I posted on, my blog shows up in the related articles section for them to choose to include or not. Would that be considered an automated program or service? Or is the policy referring to the more nefarious services that pay people/bots to leave nonsensical comments with a link?

If you, like me, have been a little confused about doFollow and noFollow policy, I hope I've made it somewhat clearer. And, again, I thank Melissa for her assistance.

Related articles

• Difference between DoFollow and NoFollow Links (differencebetween.net)
• I Yield To Google: My Paid Links Are NoFollow (seroundtable.com)
• Dos and Don'ts - Bad Link Building And Useful Alternatives (psudhir20.wordpress.com)