You mean you don't? Isn't everything on the Internet true! :)
I think the simple answer is that just like regular news media it depends on who is speaking and what research has been done - what is the quality of your source and to some extent what budget (and what is the source of that budget!) do they have finding out the answer.
There is obviously a bias in news sources - Fox News being a prime example of this and if this is known, then it can be taken into account when determining the value of the information.
Just as you cannot fully depend upon Wikipedia due to the fact that there have been more than one instance of malicious tampering, its a good starting point for information.