THE "LIKE" FEATURE on Facebook is simple in nature.  Users "Like" things, people and businesses to communicate a positive opinion of what they see.  From a marketing perspective, it may be the most powerful tool Facebook has to offer.  If you own a business and run a Facebook page, Facebook users can "Like" your page or any content you post on it, telling their friends that they like what you have to offer.
Exponential Exposure
Because of the viral nature of social networking, brand and product exposure on Facebook grows exponentially.  At the present time, there are more than 850 million people on Facebook, each with an average of about 423 “friends”.  Every time someone "Likes" your page or something on it, he exposes it to all of his friends, who then have the opportunity to expose it to their friends.
When Facebook users "Like" your page or its content, their friends will notice, either in advertisements or on their News Feeds (a bulletin board on one’s profile that updates constantly with “friends’” activity).  Since friends often share common interests, when someone “Likes” your product or business, he exposes it to other people who are more likely to have similar preferences than someone picked at random.  In this way, you naturally target the audience who is most likely to be interested in your brand, service or product.
People ask their friends when they want a second opinion about where to go or what to buy.  If someone "Likes" your business' Facebook page or something on it, he validates it to his friends.  Furthermore, when someone clicks on your page, he sees a list of which of his friends "Like" it.  Your advertisements also display to any user which of his friends "Like" your page.
Customer Community and Loyalty
Facebook users who "Like" a business' Facebook page receive updates about that page in their News Feeds.  In this way, they have the opportunity to stay informed about your business and can even engage in conversations or applications on your page.  This builds a customer community around your page and generates customer loyalty.
"Likes" Linked to More Business
The proof of Facebook's marketing effectiveness is in business website visitation rates.  People who "Like" your Facebook page and their friends are more likely to visit your website and use your products or services.  According to research by web analytics services, 2.7% of average Internet users have visited, while 12.4% of Facebook users who "Like" Carnival’s business Facebook page have visited the site and 7.1% of their friends have visited it.  Similarly, people who "Like" the search engine, Bing, and their friends consistently use Bing for Internet searches more frequently than other Internet users.