Are there any real experts any more? What does it mean to be an expert when a naif plus internet can find more and better information than that contained in the expert's mind?
Set "expert" aside for the moment, and lower the threshold to just "competent" - all of my friends who have ever shared with me their thoughts of work and success have shown some degree of concern that they are just not good at their jobs (at least on some days). I know that there are times when I feel woefully inept, at even the most basic of my job functions.
To paraphrase a conversation I had with a friend this very weekend, sometimes it seems to me that success at work could be defined as failing very slowly. That may seem cynical, but I suspect there may be a little chunk of truth to the sentiment.
At any rate, some days I want to be an expert and some days I just want not to be a charlatan.