I don't think it's related to the physical nature of it. I think it's just that it's a field that is infinitely faceted (so room for different perspectives and

I don't think it's related to the physical nature of it. I think it's just that it's a field that is infinitely faceted (so room for different perspectives and opinions) and one which many of us have a serious personal interest in. I.e., it's not JUST a job for many of us. I am one of those kids who has been a 'power' user since middle school. Now I'm a programmer. If I didn't do it for a living, I'd still do it. So what that boils down to is I have opinions that are semi-personal. A lumber-jack or a secretary probably has much less personal investment in their field. Personal interests yield opinions, and where there are opinions there are people who are aggressive about them, whether it be music, religion, sports, cars, or technology.