One thing you need to consider with user-generated content is who owns that content. Do you consider the information to be in the public domain, or does the fact that the user logged in imply permission for you to reuse his or her contribution? Will you add attribution to contributions? Is the information on your wiki under something like a creative commons license?
With an internal wiki, none of these is really an issue because all information added to the blog will be created under the terms of a typical work-for-hire employment contract where creative work and intellectual property developed on company time is owned by the company.
But with a public facing wiki, especially one where you are actively encouraging user-generated content and comments, you need to decide on your stance on all of these issues before you open the wiki to users.
Whatever your reuse policy is, you need to state it on the wiki homepage so that potential contributors are informed before they apply for a login. One approach is to develop a set of Contributor Guidelines, a full Disclaimer, and a User Agreement.
For instance, Atlassian, the makers of the Confluence wiki platform has a section on their documentation wiki clearly labeled “Contributing to Confluence Documentation” that outlines the steps and permissions needed before you can change or create information on the wiki.
Atlassian allows anyone to make changes to the developer documentation (API guides, plugin development and gadget development), provided they have signed up for a wiki username and are logged in to the wiki, but for changes to the product documentation, they ask that you first sign a Contributor License Agreement (CLA). The purpose of the agreement is to define the terms under which intellectual property has been contributed to the Atlassian Documentation Wiki, and would allow the company to defend the documentation wiki if a legal dispute arose concerning the contributed content.
Atlassian also clearly states that its documentation is published under a Creative Commons “cc-by” license. This means that anyone can copy, distribute, and adapt the documentation provided they acknowledge the source. The cc-by license is shown in the footer of every page, so that those who contribute to the documentation know that their contributions fall under the same copyright.
Before you start a wiki implementation, do some research into how people who have set up similar wikis have addressed this issue, and see if the solutions they have adopted will also work for you.
You should discuss different licensing options with your company’s legal team to make sure you follow company guidelines and practices.