That's not an observation, it's a conjecture, and one that is fairly baseless. many things operate according to a power law. If karma is like that, a small number of users will end up with a shitload of karma points even if they aren't attempting to game the system.
There are many factors that could contribute to a power law for karma distribution. One conjecture is that other users tend to "trust" high-karma users and therefore tend to upvote their comments just because they have high karma.
Another is that high-karma users receive gratification from using HN and therefore use it more. Which leads to getting more karma.
Either of the two conjectures I advanced could explain a small number of users having a disproportionate amount of Karma.
There are many factors that could contribute to a power law for karma distribution. One conjecture is that other users tend to "trust" high-karma users and therefore tend to upvote their comments just because they have high karma.
Another is that high-karma users receive gratification from using HN and therefore use it more. Which leads to getting more karma.
Either of the two conjectures I advanced could explain a small number of users having a disproportionate amount of Karma.