Pinterest is the most "shared" of the social sharing sites. 80% of Pinterest pins are repins. Which means it is the highest in shared content of all social sharing sites. Once something is pinned on Pinterest, it continues to get shared, this is what we call viral marketing.
Images are easily posted and reposting is encouraged. It is so easy to use that it is actually fun! Worse thing about Pinterest is it may become addicting.Pinterest also changed it's terms of service that eliminated the policy that gave it the right to sell its users' content. Pinterest also enabled users to be able to block other users, giving a more secure platform and community building tool.
Users posting images on Pinterest can easily notify their Facebook or Twitter followers.
Ecommerce sites are the biggest winners with Pinterest. More revenue flows from images posted on Pinterest than from Twitter. The biggest users of the site are women and most popular categories are recipe and food. However, a huge growth in all ecommerce products is taking place. Pinterest can give exposure to any product using its' "authority" and drive customers to websites offering any category of goods or service that alone would never get this kind of exposure.
On closing I would just like to say -- Pinterest is fun to use, and that alone will propel it to the top of social media sharing sites.