Here's a funny one. Imagine being able to ask a historical figure a question about life. You'd probably start with one figure, then add them as you find experts that want to participate.
Of course this only works if you can get obsessed scholars to participate... but if they're that obsessed it wouldn't be too difficult to imagine that they'd want to participate. They'd love to share their knowledge.
"What do you think? Obama or Clinton?" could be asked of a virtual John F. Kennedy. Or "What should our next move in Iraq be?" to General Douglas Macarthur.
Bracken suggested that the site pick a figure a week, then have users vote on the best question for that figure to answer... I like it.