During my job interview today, we were discussing working conditions, and the subject of dress code was mentioned. The company has a dress code - suits, however, IT employees don't have much of a dress code. About anything goes, as long as it isn't total rags.
A few years ago, the company tried to enforce a dress code on their IT department. But one guy treatened to quit his job the moment a dress code was being enforced, stating that IT people wearing suits cannot be trusted. The guy has left the company long time ago, but his statement is still often uttered in the company - even during board meetings.
I used to work at the Department of State in DC. Despite the fact that I was under peoples desks, pulling wire, in the ceiling, I had to wear a suit.