If you think about people you know, you'll find the animal test is easy to apply. And finally, since a few good hackers have unbearable personalities, could we stand to have them around?
The woman in charge of sales was so tenacious that I used to feel sorry for potential customers on the phone with her.
You could sense them squirming on the hook, but you knew there would be no rest for them till they'd signed up.
Good people can fix bad ideas, but good ideas can't save bad people. One of the best tricks I learned during our startup was a rule for deciding who to hire. It might be hard to translate that into another language, but I think everyone in the US knows what it means.
It means someone who takes their work a little too seriously; someone who does what they do so well that they pass right through professional and cross over into obsessive.
A startup that does all three will probably succeed.