If you are not familiar with FullContact check out their website at: http://www.fullcontact.com. They have a nifty service that allows developers to gather social details for an email address. For instance, lets say a customer makes a purchase at your e-commerce website. What if after they made a purchase you could identify them as a influential blogger and reach out to them and offer a discount for writing a review of your product.
I built a very basic Magento extension that pulls the FullContact API and puts the details in a table for you to view.
Note: You will need a FullContact API key to get started.