I don’t think there’s a minimum level where people flip the switch from “good” to “bad”, just varying degrees of access and power over things someone might care about, which can have an effect on the people who choose to seek or are tempted by those things.

To give you an example: moderating a forum is a very small amount of power, but for the person who is very invested in a community or a topic or a site and wants to essentially keep it on ice and under their control, moderating can quickly spiral into their own little kingdom.

For another person, running for governor is the next logical step after having been a community organizer and feeling as though they can do more for their community in that position. Have you ever encountered a problem that you know you have a good response for but you see no one else (or worse, the wrong people) doing anything about it?

I think the main thing that sets the power hungry apart from those climbing the ladder of power is where does their sense of entitlement come from? Does it come from their imagined, top down view of the world, or does it come from a variety of sources and communities who speak to and then through someone who is angered and saddened that their voices are not heard?