Search engines rank their own sites better. Yahoo Answers ranks higher on Yahoo, but not on MSN or Google. Google Answers ranks high on Google, but not on Yahoo or MSN.
This is bias, but not necessarily evil. They may just be fooling themselves.
Even scientists, the genuinely objective ones, do this. As Feynman points out in Cargo Cult Science:
Millikan measured the charge on an electron by an experiment with falling oil drops, and got an answer which we now know not to be quite right. It’s a little bit off because he had the incorrect value for the viscosity of air. It’s interesting to look at the history of measurements of the charge of an electron, after Millikan. If you plot them as a function of time, you find that one is a little bit bigger than Millikan’s, and the next one’s a little bit bigger than that, and the next one’s a little bit bigger than that, until finally they settle down to a number which is higher.
Why didn’t they discover the new number was higher right away? It’s a thing that scientists are ashamed of – this history – because it’s apparent that people did things like this: When they got a number that was too high above Millikan’s, they thought something must be wrong – and they would look for and find a reason why something might be wrong. When they got a number close to Millikan’s value they didn’t look so hard. And so they eliminated the numbers that were too far off, and did other things like that.
But, (and this is the important part):
We’ve learned those tricks nowadays, and now we don’t have that kind of a disease. But this long history of learning how to not fool ourselves–of having utter scientific integrity — is, I’m sorry to say, something that we haven’t specifically included in any particular course that I know of. We just hope you’ve caught on by osmosis.
It’s not easy to catch on, by osmosis or otherwise.