From Social Patterns
One of the most common structures for a human conversation or dialogue is the format of question and answer. Since the days of the oldest mailing lists, Usenet, and Gopher, frequently asked question lists (FAQs) have sought to answer a person’s questions with either the collected wisdom of the community or the answers from some authority.
People naturally have questions and ask them, either silently while seeking an answer or directly if they perceive an opportunity to do so (in an inviting interface or in the context of a welcoming group of helpful, experienced community members).
But this pattern is about how you, as the voice of your site, should ask questions of your users.
It’s very easy to arrive at a page or context online and not be sure what to do, how to proceed, what to say, what to type. A blank space can be very intimidating. (You should have seen my flopsweat when I started trying to write this pattern.)
An empty or silent page can leave the site visitor unsure of how to proceed.
Use this pattern when writing explanatory copy, help text, and labels on potential but currently unpopulated features in the user’s interface.
Pose suggestions in the form of inviting questions. Write copy in an inquisitive way so that the site visitor feels compelled to reply with an answer.
Questions invite responses, and asking them is a way of inviting participation.
Twitter asks you "What are you doing?" Some people get hung up on whether or not to take this literally but the point is they asked, they prompted. They're starting the conversation. They're inviting you to respond.