Stupid Questions Really Do Exist

During a recent class where the instructors kept insisting, "The only stupid question, is the one that's not asked," I discovered that this maxim simply isn't true. There were plenty of stupid questions. Don't get me wrong, learners should certainly work to understand that which they don't know, but at some point, especially in a group setting, one person's agenda can cost others greatly in productivity. We need to encourage participants to use better filters to determine whether to ask a particular question, and if so, if the timing is right.

This experience has compelled me to commence a quest to define what makes a question stupid. Below is my first draft of potential root causes.

Criteria for makes a stupid questionWhat do you think? What makes a question stupid to you? What should be added to the list?