Peanut Labs, a startup that helps companies survey users of social networking sites, has been sold to E-Rewards, which operates online market research panels. Peanut Labs embeds its targeted surveys into social networking apps in order to gather data for its clients; respondents are rewarded with virtual currency and app developers get paid per completed survey. The company had raised $3.2 million in a first round of funding two-and-a-half years ago. Back then, it said it was profitable and was projecting revenue in the “eight figures” for the following year.