On City Center Plaza's board (my condo), there are adders, and subtractors.

Adders are people who contribute to the discussion, follow up, and get things done. They handle themselves with professionalism. Adders are good board members; you want as much of them as you can get, in general.

In contrast, subtractors derail conversations, blather on with statements that are irrelevant or even incorrect, grandstand, argue, and generally make everything less pleasant, longer, and less effective than it could be.

If only it was one or the other—"that guy is a huge subtractor"—but it isn't. The biggest subtractors are also sometimes adders—simultaneously—so I think of it like two independent scores, eg. "adds 10, subtracts 3".

A 0-0 will sit there, passively, adding nothing of value, but will also stay out of the way when a good new initiative is being discussed. By contrast, a 10-10 will do a lot of work, show up prepared, but get into heated arguments about dumb things, call names, and waste everyone's time.

Ideally you'd have 10-0s across the board, but that's hardly realistic when you don't control who's in the room (politics, appointed bodies, etc.) Doubly so given people won't generally agree on what's right. I still know people I'd call big net adders, though, even those with whom I have strong disagreements; it takes more than disagreement for me to consider someone a subtractor. Incivility, dishonesty, and wasting time (especially when a lot of people are involved) get you into my subtractor category pretty quickly.

The median member of our eight-person board is about 2-0 or 3-1; moderate adder, but not much of a subtractor. We have one strong subtractor who adds little, who I try to avoid.

The trickiest case is the 10-10. In my case, this guy is very useful, but loves hearing himself talk, and gets into shouting matches with other board members. He's not around this year; things have been more peaceful, but I do sometimes miss his insights.