Wall Street Journal: Facebook users still visit the network often. But these days, they are more likely to “like” and less likely to post a note or a picture. That isn’t a problem today, but it could be one down the road. Facebook researchers said it was “vital” for social networks to encourage a broad range of users to contribute content. So the social network has placed prompts related to ongoing events at the top of some users’ news feeds, aiming to spur conversations.