Ask HN: Knowledge transfer within your company?

I'm looking to implement a StackOverflow style QA web-app for a client. They are a medium sized enterprise software company with knowledgeable people across support, professional services, sales, and development. Each department has deep knowledge across all the verticals into which we sell, but that information is relatively silo-ed.

I can see in our internal communications all of the knowledge that is lost or hidden because it cannot be easily found when needed.

There are lots of products out there (open source and otherwise). I'm looking at a few.

  * https://marketplace.atlassian.com/plugins/com.atlassian.confluence.plugins.confluence-questions/cloud/overview

  *  http://meta.stackexchange.com/a/37953

My question to the HN community here is:

Have you implemented one of these systems before? If so can you share any tip or pitfalls to avoid?

How did you sell this up the chain of command? Or did it come from upon high? (This is a bottom-up initiative)

Thanks!