Is Wikipedia a good thing or a bad thing?

Some of my friends do swear by Wikipedia (http://en.wikipedia.org/wiki/Main_Page), but stories like this (http://www.usatoday.com/news/opinion/editorials/2005-11-29-wikipedia-edit_x.htm) make one wonder: is it really as accurate as people make it out to be?

Yes, Wikipedia did seem to correct Britannica (see this: http://www.freedom-to-tinker.com/?p=675) on one occasion, but I have a sneaking suspicion that on the subjects that few care about the chance of error persisting for a long time is quite high...