I would treat about.com the same way we treat wikipedia.
Wikipedia is a collection of information from different sources, we should when possible get the information directly from the linked source and not from the wikipedia page itself.
The same should apply for about.com, just because they said it was true or that it came from a certain page doesn't necessarily mean it is true. Go to the source and reference the source directly.
Take for example this about.com article on Carpal Tunnel Syndrome; Here is how the sources appear on that page:
Sources: The Best Cure For Carpal Tunnel Syndrome Is Prevention,
Newswise, 9/20/02; Study: Surgery best for most carpal tunnel syndrome
cases, CNN, 9/11/02; Carpal Tunnel Syndrome: American Academy of
Orthopedic Surgeons - www.aaos.org
Notice they don't even provide a direct link to the information they are claiming as a source. That is even worse than wikipedia because now we are a further step away from the information.
Any studies or reports linked to in this site should link directly to the item itself and even better practice is to quote from the article itself not from the paraphrasing in the wiki or about.com page.
Consider Wikipedia or about.com as your stepping stone not as your reputable source.