TechTalk101 for dummies... How Facebook and Twitter earn?

Have you ever wondered, how social networking websites like Facebook and Twitter earn their money? Believe me.. they do need money! if not.. they would all be like the plants in Farmville withering without the help of finances. Here's how:

From:

HowStuffWorks "How do Social Networking Sites Earn"

Thanks for the info! Let's learn and enjoy!