3 questions to judge a source

How do you know what to believe on the internet?  How do you tell fact from opinion from pure b.s.?

There are three questions to ask:
1. What is this speaker or writer saying that helps me to answer my research question?
2. How is this person qualified to speak to this topic?
3. What is this person's motivation for speaking to this topic?

Most students find it easy enough to answer the first question.  The second isn't hard either, but probably requires a google search at the very least. 

The third is tricky because it speaks to different kinds of motivation.  Is this person being paid to say what they're saying?  Most likely, yes.  Does that invalidate what they say?  It depends.  What other motivations might they have for wanting to speak or write about this topic? 
There are two kinds of motivation commonly referred to in the literature which often overlap, enhance or even undermine each other: extrinsic motivation which usually means external rewards such as money or prestige, and intrinsic motivation which usually refers to the idea of doing something "for fun".  For example, I'm paid to write this blog in the sense that I work for a salary at the university and part of my job is to do research and this is one way in which I carry out that mandate.  That doesn't mean that I "do this for the money" (which honestly isn't all that great).   I also have intrinsic motivation in that I'm genuinely interested in what I write about and enjoy sharing it. 
Why am I interested in the topics I write about on this blog?  Well, if I were to probe, I'd have to say it's because I teach and I hate staring at a classful of bored students, so it's in my interest to learn about motivation and what causes or undermines it.

A researcher can't always find out all of this psychological information about a writer or a speaker online, but what they can do is eliminate any possible sources of unethical bias.  In my previous post about the Kuwaiti girl who started the first Iraq war by spreading the story of the incubator babies killed by Iraqi soldiers, it's essential to understand that as the daughter of the Kuwaiti ambassador to the U.S., she obviously had a vested interest in spreading the lie. 

When you read my blog, on the other hand, you can see that even if some of my information is unclear or misguided, I have no vested interest in deliberately lying.

Or do I?