|Why They're Hot:
There aren't many words to adequately describe a retail site that's grown to 14 million customers across 27 countries within two years. But "fabulous" is a good one for Fab.com, which launched in 2011 and is already No. 150 in the 2013 Internet Retailer Top 500 Guide. Its masterful use of social media is one apparent key to its success. By using Facebook's Lookalike Audiences tool to target consumers similar to its existing customers, for example, Fab says it has acquired customers who spend significantly more than those gained through other marketing channels. On Fab.com, shoppers find tons of unusual items neatly arranged in large images. A "Smile Guarantee" comes with free return shipping and no-questions-asked refunds. For a retailer, that's just fabulous.