If you want to be confident that information is real, you need not just verify to see if the source exists, but also to see if it says what the writer claims it says. Things may take on a life of their own once they start getting passed around. It's hard to know what you're going to get when you load up an email or post on Facebook. For example, suppose I claim to have been given access to secret files showing that NASA has been covering up evidence of extraterrestrial life. You might check with NASA to make sure this isn't true, but even if it is, that wouldn't prove my claim false. It would only show that someone else had claimed to have access to such files and had used them to write about something else entirely. The same thing would happen if I claimed to have been given access to secret files showing that NASA has been covering up evidence of alien life. In other words, to determine whether or not my claim is true, I need to look at other sources to make sure no one else is saying the same thing. If they are, then I need to ask myself why they would do this.