QF is no different than other areas of engineering, like programming, where there is some exchange of information about methods between professionals. You can exchange a lot of information without revealing a specific trading strategy. Also there are usually auditors and risk managers that need to understand what is going on in a position and QF provides a language to describe the reasoning behind why a trader has a certain position.

I don't know about that. I read and discuss algorithms in the Wilmott forum. http://www.wilmott.com/index.cfm

There is actually alot of useful traffic that goes on there. Having said that, the Wilmott forum acts more like mathoverflow than stackoverflow in it's non tolerance for basic questions.