That's some basic NLP right there...

Tricks of the Trade: Trainer:

"If you want to get people to participate in a workshop or presentation, ask them 'What questions do you have?' and wait for someone to answer. The usual 'Any questions?' acts as a participation deterrent, as it requires the questioner to be a speed bump in the presentation. 'What questions do you have?' implies that participants are expected to say something, and they often will."