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.
For example, dating sites currently suck far worse than search did before Google. They seem to have approached the problem by thinking about how to do database matches instead of how dating works in the real world.
An undergrad could build something better as a class project. Online dating is a valuable business now, and it might be worth a hundred times as much if it worked.
They had three new ideas: index more of the Web, use links to rank search results, and have clean, simple web pages with unintrusive keyword-based ads.
Above all, they were determined to make a site that was good to use.
An idea for a startup, however, is only a beginning.
A lot of would-be startup founders think the key to the whole process is the initial idea, and from that point all you have to do is execute. If you go to VC firms with a brilliant idea that you'll tell them about if they sign a nondisclosure agreement, most will tell you to get lost. The market price is less than the inconvenience of signing an NDA.
You could sense them squirming on the hook, but you knew there would be no rest for them till they'd signed up.
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?
What matters is not ideas, but the people who have them.
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.
Most startups that fail do it because they fail at one of these.