From the Snopes FAQ :

Q: Is everything on this site about 'urban legends'?

A: In a strict folkloric sense, no. Urban legends are a specific type of folklore, and many of the items discussed on this site do not fall under the folkloric definition of "urban legend." We employ the more expansive popular (if academically inaccurate) use of "urban legend" as a term that embraces not only urban legends but also common fallacies, misinformation, old wives' tales, strange news stories, rumors, celebrity gossip, and similar items.

...and...

Q: How do I know the information you've presented is accurate?

A: We don't expect anyone to accept us as the ultimate authority on any topic. Unlike the plethora of anonymous individuals who create and send the unsigned, unsourced e-mail messages that are forwarded all over the Internet, we show our work. The research materials we've used in the preparation of any particular page are listed in the bibliography displayed at the bottom of that page so that readers who wish to verify the validity of our information may check those sources for themselves.