Check out this article, titled 2010: The Year Social Marketing Gets Serious.
The gist is that social media is going to become an increasingly important part of marketing strategy. Rather than just being a side project, marketing through channels like Facebook and Twitter are going to be as serious as more traditional marketing strategies like print advertising. Expect to see more structured strategies, bigger budgets, and analytics to track the initiatives.
What do we mean by "social media?" Well, Facebook and Twitter are two of the most visible examples. The easiest way that I've found to explain the idea of social media, is to talk about who is creating the content. Places where the users create the content, like Facebook and Twitter, but also sites like YouTube, Flickr, and countless blogs and forums are social media sites.
Of course millions of people are spending significant amounts of time on those sites. Read the article to learn more about how businesses are going to start getting serious about using them as marketing tools.