Link building is a major part of SEO and that can be done through many ways. Buying links is one of them and most of the webmasters do this for two purposes mostly. Some of them wants to build true backlinks to get higher ranking in SE and others buy links to up their Page Rank.
We know that the Buying links can gift a huge number of backlinks very quickly as compared to the organic method of backlink building but this can be very dangerous for your website that can be penalized by Search engines. Google has officially announced already that if someone buy backlinks to just increase Page Rank or to use these links for spamming, not only these links will not be count for SEO purpose but he will be penalized by the Google.
It does not means that the links, that someone buy, are used for increasing PR purpose. However you should aware that google has very powerful Link Detection strategies. For example If you are overcrowding your Blog Roll or you have gained a very large number of backlinks in no time, then Google can consider this as spamming or they can penalize your website due to violation of their TOS.
So far we have discussed the demerits of buying links but it does not means that we should not buy links. Links are still valid for the ranking but we should keep in mind that we make our links as Google wants. Google has defined very well for those who buy links can make their links valid by (Full Detail)
- Adding a rel=”nofollow” attribute to the <a> tag; or
- Redirecting the links to an intermediate page that is blocked from search engines with a robots.txt file
So, we conclude that we should be aware of the right method of buying backlinks and using them in an SEO friendly way otherwise you may get banned from Google.