There's that old saying that if at first you don't succeed, try, try again. Back in February of 2004 I installed wiki using the MediaWiki PHP engine, the same one used by Wikipedia, thinking that it could be really useful for our team as a living knowledge repository. The uptake was very slow and it took over a year before it gained any traction at all and another 6 months before it really took off.
The wiki now has roughly 100 registered users, nearly 1500 content pages and over 40,000 page views and is used for everything from meeting notes, formal and informal design reviews, test framework documentation, FAQ's and project status information among other things. Each team R&D, QA, Integration and Documentation has it's own area on the front page where they can communicate the most relevant information.
If you're interested in a wiki for you're team I'd probably recommend ScrewTurn Wiki as it's super easy to setup and get started immediately. I'd probably say MediaWiki is overkill for most small wiki's but it's certainly an option.