Yeah wikipedia can be really useful at times but can only be used as a reference. The information on the site isnt a 100% accurate. There are many mistakes on there and information is mostly incomplete or not indepth enough, but it is a good starting point for people to gain some info on a certain topic. Manga and Anime on wiki is kinda an area with alot of errors in there, many non speaking japanese will look at the raws of the manga and misinturpretate the situation and type in incorrect info. An example of this has been on Air gear. There are also areas which arnt complete or lack depth like Mx0, pretty face and a few others.
Granted that its not controlled by one person and that you can get input from various views, if the person who first inputs incorrect and biased info up on the net. it may defer people from actually reading/watching/playing/seing the item in question. Never use it as a sole source of information and only use it as a guidline is the best thing.
Mx0
is completed ,in japanese
but...not in english becasue there is no stronge offical source the base on XD