Wikipedia editing can also be great practice for online searching for a librarian. We often teach students about the importance of citations, but we can practice it ourselves in Wikipedia articles actual people may read.
On what to tell students about Wikipedia:
I usually tell students that Wikipedia is a great place to start researching a topic they are unfamiliar with, but by no means should they cite it as a source.
When I get the chance, I'd like to have a citations workshop for adding citations to Wikipedia. It's a great way for students to learn to conform to citation styles and also to let them feel they're contributing to the world of knowledge.
I met another librarian who plays a fun Wikipedia game with her students: the challenge is to get from X article to Y article using only internal Wikipedia hyperlinks.
Extra: Wikipedia's 'dirty little secret' that helps us all
A community "of about 800 people has emerged to curate and administer Wikipedia as needed. These administrators are granted special priveleges: undoing a vandal's work by reverting pages to previous versions, freezing pages that are rapidly flipping back and forth in an edit war, even banning a contributor because he repeatedly restored edits without explaining why.-Weinberger, David. (2007). Everything is miscellaneous: the power of the new digital disorder. NY: New York. p.139
This type of hierarchy may be anathema to bottom-up purists, but without it, Wikipedia would not work."