Social Networking means joining/building communities of people with similar interest or even not so similar interest but wanted to explore others interest and activities. Since network building and relationship is the key to every marketing strategy, it becomes obvious that marketers are utilizing these social networking platforms with vested interests that can be brand building, brand promotion, traffic driving, user acquisition or anything else. Some of the popular social networking sites are: Orkut in India and SA. Facebook in U.S, UK and India, Myspace in US and the list is endless.
Social Bookmarking: This extends your ability of bookmarking on your personal computer and accessing it from anywhere in the world as your bookmarks are available on web through these social bookmarking sites delicious, digg, stumbleupon, reddit, etc.
Social bookmarking helps in link building but that doesn't mean you create your 100 ID's on social bookmarking sites and bookmark your pages. It can work only when you content is worth bookmarking and people bookmark it genuinely from various geographies or multiple IPs.