The idea is that this tag can be used to negate the power of the link vote for link popularity when the webmaster is linking to what is often called a "bad neighborhood". This may be seen as a suggestion by Google, or it could be Google's way of popularizing the nofollow tag so it is used by webmasters for their own paid text link ads on "By adding rel="nofollow" to a hyperlink, a page indicates that the destination of that hyperlink SHOULD NOT be afforded any additional weight or ranking by user agents which perform link analysis upon web pages (e.g. search engines).
Typical use cases include links created by 3rd party commenters on blogs, or links the author wishes to point to, but avoid endorsing." The original idea behind this tag was focused on decreasing link and comment spam, particularly for blog UK Phone Number Database List sites. When you purchase text link ads webmasters should be aware that the rel="nofollow" tag may be present in the link page source code, thus the link may end up being worthless in terms of ranking. The Real Problem How do the search engine algorithms differentiate between a simple text link and a paid text link ad?
The real problem may lie in the probability that Google and other search engines are unable to differentiate between regular links and paid links, such as text link ads, within their current algorithms. This creates a great deal of work on the search engines part to track and understand the true motivation for a link on a page. Certainly the issue may be raised that webmasters who sell text link ads may cut into the business model of the search engines text ad programs.