I totally agree that a wiki is a good idea and will compliment, not compete with sites like GovLoop.
A couple thoughts and some questions.
- Just a personal opinion, but I've always found MediaWiki ugly and hard to navigate. We use DokuWiki in our agency.
- I don't trust "the cloud" or a site like Wikidot. What assurances are there that a site like Wikidot will be around next year or next month? Wikidot charges a fee once your Wiki get's so large so who's going to pay the fee? Who hosts GovLoop, and how is the information here backed up in case of ISP failure or bankruptcy?