Search Engine Optimization nowadays has a lot to do with building inbound links to your website. Building inbound links is a cumbersome tasks and webmasters have always been looking for shortcuts to do this. Webmasters buy links (as advertising as an example) or contact other webmasters to exchange links with them. The need for inbound links has created a new business opportunity in the search engine optimization industry. The outsourcing of link building emerged from the fact that many inbound links mean a high search engine ranking and/or a high Google PageRank.
There are many different ways of building inbound links. Outsourcing this tasks can save the webmaster a lot of time but it comes with a price tag. Businesses offering to take over the link building process often maintain and operate a large network of domains and websites and just add 'your' link to their sites. These sites are often referred to as link farms.
Others buy links on 3rd party websites for you. They often have build up a portfolio of websites/webmasters they work with. The quality of these links is often questionable and a long-term benefit does not exist. It either continues to cost the webmaster money to keep the links alive or his website might get punished by Google and other search engines if the linking websites are recognized as part of commercial search engine spamming. Punished means that either the link to a site does not have any value at all or depending on the situation the site linked to gets removed from the search engine index (worse case scenario) if other factors are involved that lead to the conclusion that search engine spamming is going on.
Outsourcing of link building also takes away the control of who is linking to a website from the webmaster. The webmaster usually just pays for X number of links but there is no option to have industry related websites link to his site (= increased value of a link). It is also difficult to verify how many links to a website have really been established from the service provider. Another difficulty is to verify how long the established links are staying in place. The danger of being over-charged is very high.
Since link building has become a profitable business opportunity search engines are aware of what is going on and are putting countermeasures in place. These are not things visible to the webmaster or explained on the search engines website. These are factors that are worked into the algorithm. Search engines use the human control factor more and more often to increase the value of the search index. Chances are that if a webmaster uses an outsourced link building strategy that at one point the campaign value goes south (turns sour).
Inbound link building should be an organic process that shows a slowly increasing number of links pointing to a certain website. Getting a high number of inbound links within a very short period will raise a warning flag at search engines. Honest webmasters will stay away from these tactics to avoid putting the success of a website at risk when there are better ways of building inbound links.