Why do strong critical thinkers fact-check the information from online sources like Wikipedia? ...

Web pages and blogs can be posted by reliable and informed experts and by unscrupulous people bent on fraud, hate, or mischief. Truths and falsehoods spread as people cite other Web pages as their sources, as they e-mail URLs to friends, and as they post, blog, tweet, and comment about things they have seen on the Web. The Internet and sites like Wikipedia are not sources of knowledge; they are vehicle for posting information. Certainly some of what we find in Wikipedia or on the Internet is solid information and good advice. But anyone can edit a Wikipedia entry or post claims, opinions or advice on the Internet. Just because we see something posted does not prove that it is actually true, helpful, or wise. It might be a lie; it might be incomplete or inaccurate, or it might be faked or intended only to confuse or take advantage of uncritical or uneducated visitors. That's why we fact-check.