A Wiki Rookie!

My wiki experience is based solely on my use of Wikipedia, so the prospect of designing a wiki for my library (say the University of Georgia Main Library) is daunting. My first question would be, "Why does my library need a wiki?" and frankly, I am somewhat stumped. Wikis allows users to both read and contribute information on a given subject and the wiki is designed to be edited continuously over time. While I've seen several sources report that wikis can play a role in library services, I'm not sure why a library would want patrons or non-library affiliates to contribute to their information.

That being said, I experimented with the WikiMatrix Choice Wizard with the University of Georgia Main Library in mind. I figured that page history, WYSIWYG editors,  and Wiki software (as opposed to the hosted option) were important features for this Wiki, but only narrowed my pool of choices down to 70 potential wikis. Even if I had narrowed it down to two, the factors by which the wikis are compared are overwhelming. I'm not sure what kind of wiki my library would need in terms of data storage, hosting features, system requirements, or a wide range of other things. 

I come away from this part of the assignment with more questions than answers, but of course that's not a bad thing. I would be interested to hear from my classmates concerning the role of wikis in libraries.