That's the question posed recently on the LinkedIn Answers: Conference and Event Planning Group. It's a good question, and one that deserves more thought than it usually gets. So far, the problems people are pinpointing include:
A lack of purpose or goal
No real structure
Uncomfortable physical space/inappropriate space
Lack of control of attendees (not listening, babbling, one person taking over, etc.)
Lack of buy-in/participation from senior execs
When they don't actually accomplish anything (which is my biggest gripe)
What do you think? More to the point is how to make them better?