Does anyone have any pointers for getting your employees to utilize a Wiki?

We have created a Wiki space for one of our most popular classroom courses (David Allen's Getting Things Done) and would like to give our graduates the opportunity to ask questions, collaborate on best practices, etc. So far we have one person who has made use of the space!

Thanks for any tips you might have!

How are you currently marketing it?

What benefit does it provide to those who participate?

It could be that people are just too busy to collaborate about a classroom course that has ended. Why not try to get them to collaborate on best practices right there in the classroom during the class? I know technology is great - but sometimes it just doesn't fit the circumstances or needs of the employees - or is used inappropriately at the wrong time.