Exactly. People who dismiss Wikipedia because of its inaccuracies often forget about what we usually did *before* Wikipedia existed: We made stuff up based on our intuitions, *maybe* talked about it at a coffee shop with a small number of our friends, and believed it as fact. Sure, if we were doing academic research, we were more rigorous (and that's improved, too, IMHO), but how often did that happen? Now, with portable devices that can access the WWW, our first reponse when we're not sure about something is often to look it up.
I can't emphasize this enough: Instant access to the web is resulting in a culture shift from making stuff up to looking it up, and Wikipedia is the most important place where people go to do that.
So, yes, even though Wikipedia is a repository of groupthink (and the critics are right that we mustn't forget that), it's groupthink that takes into account the views of a much larger number of contributors, and is much more accurate than the groupthink of a small, isolated group of people.