Yes and no. In one study by Nature magazine, the accuracy of Wikipedia articles on selected topics was found to be roughly comparable to those found in Encyclopedia Britannica. This is not to say, however, that we should consider Wikipedia to be a perfectly reliable source (particularly on issues not controversial enough to encourage large-scale fact checking). Rather, if we look closely at the results of the study, we can see that researchers reached this conclusion after finding that both Wikipedia and Encyclopedia Britannica were roughly equally flawed.
In response, some educators advocate cautioning students against using either source and direct them to only use primary sources. Others complain that such instructions simply go in one ear and out the other, with little success getting students to internalize the importance of primary sources.
Perhaps the best way to get students to realize that all secondary information is interpreted by human beings and therefore subject to bias or negligence, is to engage students in the actual process of creating such articles. Once students are able to step back and say "Wait, just because it's in Wikipedia doesn't mean the author knew what they were saying; *I* put stuff on Wikipedia" it becomes easier to then teach students skills for assessing the accuracy of online content, such as monitoring the number of peer revisions a particular article has or following links to primary sources.
We also do not need to be overly concerned with students disrupting Wikipedia for other potential viewers by experimenting with create content on a live website. If they make poor contributions to an article which is actively read, their contributions will likely be undone quite rapidly. For example, try for yourself to make an edit to the page on global warming. In this way Wikipedia/Wikibooks offers novices the best possible balance between allowing them to make genuine contributions to one of the most highly visited websites worldwide, while minimizing to the best degree possible the impact of any poor quality materials they create.
Ideally curriculum designers should challenge themselves to take advantage of APIs and other technologies to create flexible curriculum that can adapt to handle changes. However, this will require a fundamental shift in how we conceive curriculum and likely take time before robust models emerge. In the mean time, simply follow these instructions to link to create links to a specific version of any page. (Similarly, for non-wikipedia sources requiring fixed content, link to the version in archive.org.