In the below picture, some data about the growth of Social Networking.
Each year, more people engage in conversation online, via social site and social tools – at a rate of about 30% per year.

From a marketing point of view, What Does This Mean?

Companies’ communication strategies have to be rethought because of market evolution and consequent changing in consumer behaviors, especially in new media such as Internet and Social Networks. They have to fine new ways to attract the active attention of their audience.

In modern markets people don’t want to be reached by undesired messages, that are immediately marked as spam. In addition, they are so used to see advertisement that it is almost useless. All this means that Push Communication doesn’t work anymore, so Companies need to find new ways to communicate: using Pull Communication, a Company makes its customers looking for its messages.
There are many instruments to facilitate Pull Communication: Social Media Marketing (maybe in conjunction with advergames) is becoming one of the most important; another important new instrument is mobile marketing (better if in conjunction with useful mobile apps development).

Social Media is NOT just a TREND