You hit the nail on the head - Why share knowledge with the organization if it stays with the organization when I leave?

The answer, then, is to let your knowledge workers post their expert advice on their own web sites, LinkedIn profiles, Facebook, Twitter, etc. Then if someone in the organization needs the knowledge, they link to the external resource.

The objection by the organization is that if they allow this, then they run the risk of their "secrets" becoming public knowledge and they lose control of it. However, if the organization's most valuable asset is its people, then this isn't really a risk. They are only giving away their assets output and only a fraction of that. The other risk is that once the person leaves, then they no longer have access to the assets that person publishes.

In actuality, the reverse is true. Even if a person leaves, as long as their knowledge is in the public domain, the organization will always have access to it, whether they pay that worker or not. In short, they can retain access to an asset if they set it free!