Starting today, Facebook is pushing developers to interact with users directly through their personal e-mail. This is a big change in how applications notify users of updates or new turns in games. Users will have to explicitly provide their own contact information.

Although Facebook gave developers several months of lead time through a roadmap the company presented last fall, it’s not clear yet how much this will change virality for apps across the entire ecosystem. Facebook has already rolled out a few changes so far, including retooling the news feed for updates that attract more user activity. So far those haven’t affected the biggest players like Zynga and Playfish too dramatically, according to Inside Facebook. Constant optimization has actually helped Zynga’s number of monthly active users rise about 5 percent.

Facebook is trying to hold up a few companies as examples of how direct e-mail works best. Living Social, which offers group deals, has been using e-mail for its Visual Bookshelf app for two years, driving about 10 percent of traffic to the application. Sending people personalized content, like a list of books they’ve recently read or that friends are reading, helps push click-through rates higher.