Marketing used to be done at a company's headquarters, where a department full of creative people crafted the message about each product. Today, progressive companies are realizing that their success depends more and more on what others are saying about them in the social media arena - places such as Facebook, Twitter, and LinkedIn.

This trend has been underway for years, but community review sites such as Yelp! gave it a huge boost in the early part of the decade. Google, Bing and Yahoo! also offer community reviews, as do many of the more insightful online merchants.

The latter part of the decade has seen the addition of another form of social marketing. These "Flash Marketing" sites offer daily deals on products or services at tremendous discounts. Although one can sign up to receive the deals via email, which is a good way to assure one never misses a deal, this form of marketing saw its biggest growth spurt when the deals were passed among circles of friends via Facebook, which launched both LivingSocial and Groupon into the growth stratosphere by 2010.