What ever field if we take,we are experiencing both positive and negative results in our daily life. Now a days,people has been following two types of optimization.
In white hat optimization,webmasters will optimize their sites by following rules and regulation created in the search engines.
But the webmaster or people will follow the black hat mainly for making money. But it will not helps in promoting the website permanently. It is the unethical way.
Obviously, buying and selling of links is one of the main process following in the black hat seo,against Google webmaster guidelines.
Cloaking is another one main method used to following in black hat optimization. Content will be displayed depends up on the visitors. For user it will display a page,for search engines,server will display the different page.
Avoid Black hat optimization
Google will punish the people who they are following the black hat optimization,either by reducing the rank of their site and completely eliminating their data base.
Hence,it is recommended not to follow black hat optimization.
Instead of that,you can follow search engines rules and regulation and promote your website permanently and honestly.