If I do a random walk on en Wikipedia, almost every page seems to have some tag needing something ("This page is in need of <insert your pet peeve here>"). This reminds me of all these "under construction" pages in the earlier days of the web.
There is a very important difference between the two, though. The "under construction" pages are an excuse for a lack of content. They were supposed to show to the visitor that someone's working on it and that it'll be ready "Soon™". The Wikipedia tags, however, are an invitation to participate, i.e. a request to someone else. They are a productivity tool, and they are meant to help improve the content, not the visitor frequency.
Timwi