We have an on-going discussion at work about the reliability of wikipedia. There are those who believe and those who remain to be convinced. In 2005 Nature carried out a study that showed that wikipedia was almost as reliable as the Encyclopedia Britannica. Then again amongst scientists Nature has a dubious history of reliability - cold fusion, memory of water etc. As for the comparison Encyclopedia Britannica - this is where many of the wikipedia entries originate, and the point of wikipedia is to be more up to date than you can achieve in print. The Isuzu experiment showed that errors are corrected very quickly - in a matter of hours.
This evaluation of wikipedia was in response to a number of high profile errors found on the site. Often these were in biographical entries about living people and so these could be easily verified. A more recent example was with the obituary of Ronnie Hazlehurst where he was associated with writing songs for S-club 7. As well as revealing errors in wikipedia these also reveal sloppy journalism that is obviously using wikipedia as its only source for reporting some stories!
These are jokes -little bits of vandalism put in by geeks to see who is watching. For me they are amusing to see what people will believe - April Fools jokes like the Spaghetti Trees.
What is interesting is the communities which consider wikipedia reliable and those which do not. I am in a science department and if a student wants a reference resource then we often tell them to use wikipedia and we consider it quite reliable. However the humanties and liberal arts are the skeptics, and they have a point.
While wikipedia is reliable for facts - these can be self-correcting, theories and view-points are not so well presented, as these depend on the authors stance. Wikipedia requires objectivity but in many cases this is not possible as the disciplines require the individual to take a personal view and where many alternative views might exist. In these cases there is no right or wrong there is a relativism based on argument and the best you can do is hope for articles that present both sides of the argument as objectively as possible.