Wiki Answers can be reliable, but, depending on the content, it may not always be correct. Because all of the answers can come from any user, readers must always have some level of skepticism when perusing the provided answers.
Wiki Answers allows users to vote on answers that other users provide to indicate whether or not it was helpful. This process brings some credibility to the website. If a person comes across a question that has multiple users finding the answer helpful, he can usually feel confident in the answer. On the other hand, if a person comes across an answer that either has no votes or users that say the answer was not helpful, then the answer may not be reliable.