This often happens in certain industries, such as the health and fitness industry. Free samples will be given in exchange for a link, or other free products will be given in exchange for a link. Alas, it is usually not possible to identify such an affiliation because the blogger does not report their affiliation with these types of links. "Sending someone a 'free' product in exchange for writing about it and including a link" This is not only a violation of Google's guidelines, but if the fiduciary relationship is not disclosed properly, it is also a violation of
FTC guidelines according to their "Guides Regarding the Use of Endorsements and testimonials in advertising. Non-compliance with the instructions: "Excessive link exchanges" Basically, a link exchange means "link to me and I'll link to you". These also include fax number list partner pages created exclusively for the purpose of cross-linking. A good example of this is any site in any industry that acquires links from partners who also link back to
the blog just for links, and nothing else that would add value from an SEO perspective . Failure to follow guidelines: "Large-scale article marketing or article publishing campaigns with keyword-rich anchor text links" One way to identify these types of links is to see if they are from an obvious article marketing site (anything with the word “article” in the main domain is usually a good guess). Guest posts will be a little less obvious and generally unidentifiable unless the guest comes right into the post and says, "