Most people think they are better than average drivers. Ignoring potential problems with the definition of "better" and whichever average is being used, this shows that people see the world through rose tinted spectacles. And by "rose tinted" I mean "I am awesome and this is all someone else's fault" spectacles
Can this hurt your online marketing? Undoubtedly; in the same way that making bad decisions can hurt anything that you do.
Is it easy to avoid or fix? No
Peer review is how science tries to overcome the bias of an individual but this is not always realistic in a search engine marketing context. The peers who I could get to look over my work are all employed at the same company doing the similar jobs to me. In many cases their biases will be the same as my own.
Another problem is that this kind of thinking can lead to "analysis paralysis" where nothing is done because we cannot be sure enough. SEM is not hard science (or even soft science) so expecting the same level of proof will only lead to disappointment and confusion.
So what is the solution? I don't know. Currently I am trying to train myself to be less biased and more rigorous in my thinking. I get a little thrill every time I spot a negative thought pattern in myself or others and I believe that I am making fewer mistakes. However, I know just enough to be worried that I haven't caught everything. What percentage of people think they are less biased then average?
Wikipedia has a list of cognitive biases. Over the next few weeks I will blog about mistakes I have made that have been caused by an item on the list and what I think could be done to prevent it happening in future. In most cases the answer will be to create a process or checklist and then follow it but I still think a few examples will be instructive: