From a 2005 article on How To Use Wikis For Business by Ezra Goodnoe in InformationWeek:

Wikis are structurally capable of handling conversation, but it is not their forte; instead, wikis excel at collaboration. They are intended to maintain a series of unique documents as their content evolves and to provide an organic means of organizing that information.

For a four year old quote, this is still very descriptive. Their ability to handle conversation has been refined and improved, but their core ability to handle interaction and collaboration on the contents of documents is still as strong as ever, because it is elegantly simple.