From a private large law firm knowledge management gathering, here is a near real-time report on Engaging Lawyers in KM. 

What motivates lawyers to participate in KM efforts? Research shows that extrinsic motivators (e.g., money or recognition) do not lead to better results for cognitive work. Instead, you need to focus on intrinsic motivators, for example, purpose, mastery, and autonomy.

What are the intrinsic motivators in a law firm? Examples might be
– working on a project of one’s own choosing
– exploring a new interest
– opportunity to get deeper expertise
– psychic reward of teamwork (for anyone who is social)
– doing the right work because it matters

So, the answer to get content is not offering Starbucks cards. Use extrinsic motivators for adding content and reviewing document; use intrinsic motivators for creating content and revising documents.

An alternate theory is that the environment affects behavior and so you have to create an environment that encourages engagement. For example, consider grocery store lay-out (staples at back so you have to walk through store or shelving sweet cereals at child eye level). Are there variables one could change in law firm environment that would encourage KM engagement.

Yet another theory is tha the interface affects behavior. See for example by Volkswagen.

A different perspective, from a 2nd panelist: Need to use extrinsic motivators with lawyers: fear, humiliation, shame, sense of crisis, desperation. Bottom line: wait until lawyers are in a panic or in a jam, help them, then they will seek you out in the future.