The problems come when the author believes this about themselves. They probably are smart, and Adams' work is enjoyed because he cleverly recognizes and points out stuff that resonates with people. When this is strongly reinforced, too much, too long, I think it's really unhealthy for some people. Adams seemed to need to show that his thought could not be constrained by convention. He got strong, addictive attention for this. He wanted to be thought of as smart, rather than good.
I think the antidote, or at least a protective, to this is being surrounded by people who impress you more than you impress yourself.
[Edit: removed a couple of examples of other smart people to avoid stimulating their fans and haters]