Why do people think Wikipedia has absolutely no credibility @ all?

It's because in the past Wikipedia was not reliable. Nowadays it's extremely good, but most people remember Wikipedia as that weird thing that had a picture of a rhino for Miley Cyrus.

Or, more essentially, it's the basic fear of the not understood. People don't understand Net 2.0 concepts (Wikipedia, this site, Stack Exchange) and so dislike them and refuse to give them credit. You want to do us all a favor? Teach your kids otherwise.

I don't think that Wikipedia has no credibility. It is highly popular on the internet and get millions of visitors every month. Of course, some articles may not be giving proper information. But it just happens and it's natural. The editors there are really good at keeping only correct information on Wikipedia.

The credibility issue comes from almost anyone being able to write on it. Wikipedia does a good job at stopping stupid and false things from being posted, but it is still a possibility. What percentage is inaccurate? That is impossible to say, and that is why it is not seen as credible.

The only people I've ever heard say they think it's totally not credible is librarians because they're threatened by the free availability of high quality information at home that people used to need to pay them to organize stacks of dead trees to access.

It's a great source for basic background on almost any topic in my experience.

It's useful for getting day-to-day info and even to help you do research. You just can't use at as the basis for academic or journalistic research because it is a tertiary source and the information is not verified by experts in the field.