Marketers who use Facebook apps to collect data from prospects must be aware of the ins and outs of Facebook permissions. “Facebook Permissions are a Facebook feature that allows the social network and businesses that use Facebook for marketing purposes to collect information about users.” For starters, marketers should note that (according to a Facebook product engineer) with each data field a business asks for online, the opt-in rate declines by 10 percent. Here are five things marketers must know about Facebook Permissions and asking for customer data: 1) collect the minimum, 2) ask for everything you want (but make it optional), 3) use what’s available, 4) make it worthwhile, and 5) do your customers a favor. (Social Media Examiner)