Social Media Marketing is growing extremely quickly. I saw some figures that showed Facebook and Twitter usage triple and quadruple, respectively, from 2008 to 2009. As the cost of print / media advertising continues to rise due to decreased circulation, inflation, poor economy, etc, more businesses are turning to networking. With businesses of all sizes cutting budget, free services like Facebook and Twitter are the media that everyone is turning to for information and communication to customers.
At this point I don't think anybody can predict how far or how big they will get or what other social media outlets may arise.
