Links become highly relevant when they are coming from sites that exhibit strong popularity and importance. Take for example a website such as Wikipedia. This highly popular site has perhaps tens of thousands of various sites linking to the site. This is a strong indicator that a site like Wikipedia is indeed a highly popular site. To be considered an authority site with high levels of trust by search engines, a website must enlist the assistance of linking partners that show a high level of popularity.
Popularity can be Topic Specific or Local
The Tahoma search engine was the first such engine to introduce the idea of local popularity. The idea of local popularity is that links arriving from websites found in a topic specific community are more heavily weighted then those from nonspecific sites that are unrelated and off topic. One clear example would be that if your website sells herbal remedies, gaining links from a professional herbal medicine authority site would have far more value than gaining links from a home improvement store website which would be clearly off topic.
The Text That Anchors
Anchor text plays a critical role in how search engines rank a particular website. When many links point to a particular page with relevant keywords, the page will likely have a good chance of ranking high with regard to a specific phrase in a given anchor text. Examples of this are clearly visible when, for example, the term "click here" is entered into a search engine, where much of the results rank strictly because of the anchor text of specific inbound type links.
Rank By Trust
Spam is rampant throughout the Internet and some studies have suggested that possibly 60% of pages located on the Internet are indeed spam. To filter through this large amount of irrelevant information search engines use methods to measure trust. Much of this trust measurement is established by the link graph. Website domains with .Gov and .Edu and .Org will generally carry a very high trust rating. Gaining links from these types of sites will largely increase a websites trust metric.
Choose Your Neighborhood Carefully
A website with a large number of spam links will generally be a site that delivers spam. Search engines through complex algorythms are able to determine the level of spam that a website is likely to have based on the number of spam links it contains. The back-and-forth action of links between spam-type sites creates a sort of neighborhood environment. Choose your link neighborhood carefully to avoid penalties from search engines.
Site popularity is always rising and declining over time on the Internet. When a highly popular site shows a decrease in links pointing to that site, its popularity may indeed decline over time. The rate and frequency of link building plays an important role in search engine optimization of a particular website. This concept is often referred to as "FreshRank" and is factored into determining a website's popularity and overall relevance.
Social Media Sharing
in recent times there has been and exponential rise in the volume of content shared among social media outlets such as Facebook and Twitter. It is important to note that search engines view social media links slightly different than standard links. There are various opinions about how search engines interpret links coming from social media, however the relevance of social media links is becoming more important with time.
Social Media Sharing is Powerful
How Social Media is Indeed a Game Changer
The last few years, and notably the years 2011 and 2012 have seen a dramatic increase in the effects on search results by social media type sharing. In fact, Google has recently included social metrics into its search ranking results. This also incorporates delivering personalized results to users that comprises content shared by individuals social media circle. These results may not receive a top ranking but are still promoted because of their social value.
The move towards social media as a way of search marketing is quite substantial. Individuals with considerably sized social circles are more inclined to see their information delivered in search results. This is useful to publishers in that content can be shared by popular individuals with a large number of followers.
Links -vs- Social Sharing
These two should not be confused and are simply not the same. While there is some proof that social sharing may indeed have an impact on ranking, at present standard links are regarded as a better and more definitive way of building popularity of a website than any other means.