You might want to consider implementing a wiki if:
You want to establish a company intranet quickly and cheaply without sacrificing functionality or security.
You want to publish a range of business documents in one universally accessible location and let employees manage those documents with a minimum of effort and risk of redundancy.
You want to manage and organize meeting notes, team agendas, and company calendars.
You need a project-management tool that's cheap, extensible, and accessible through any Web browser.
You need a central location where shared documents can be viewed and revised by a team.
A wiki might not be right for your organization if:
You need to use complex file formats. Some wiki platforms can support only text or HTML files. Consider using a PHP/SQL-based wiki platform that can handle more robust file types.
You don't have staff who can take responsibility for its use. You'll need somebody who can establish conventions for naming pages and maintaining links. Documents can get "lost" if links aren't properly maintained.
The collaborative format isn't right for your group or workplace.
You're looking for an exchange of views. Although most wikis do include a comments area, they're not the best tools for airing opinions or carrying on conversations. If that's your primary goal, use a blog instead.