Facebook introduced Facebook ads which promises to turn their tremendous growth into cash.  They described it as:

an ad system for businesses to connect with users and target advertising to the exact audiences they want. Through Facebook Ads, these users can now learn about new businesses, brands and products through the trusted referrals of their friends.
 
and:

Facebook’s ad system serves Social Ads that combine social actions from your friends – such as a purchase of a product or review of a restaurant – with an advertiser’s message. This enables advertisers to deliver more tailored and relevant ads to Facebook users that now include information from their friends so they can make more informed decisions. No personally identifiable information is shared with an advertiser in creating a Social Ad.

Social Ads can appear either within a user’s News Feed as sponsored content or in the ad space along the left side of the site.

Will this prove to be the home run that adwords was for Google? Time will tell, but I wouldn't wait to test the waters.