In the earliest days of MathOverflow, there was a '20 questions' seminar (see <http://sbseminar.wordpress.com/category/20-questions/>) run by graduate students at Berkeley. Many questions from the seminar were cross-posted to MathOverflow. This tag now exists solely for the historical record.
In fact, sadly MathOverflow killed off the 20 questions seminar, as everyone realized that MathOverflow was an even better place to put all those questions!
