Knowing the tools of the trade
Richard Rutter chimes in on the continued debate sparked by Elliot Jay Stocks:
There needs to be a common vocabulary and understanding of all disciplines. Conversations are required; discussion and compromise. The best compromises are reached when both sides understand the issues of the other. —Richard Rutter
I agree with this 100%. I am in the camp that a web designer should know HTML/CSS. Even if they never have to build out a site, it gives them knowledge and insight into how to find the right people to do the job.
What I like most about his quote is the need for a common understanding. I can apply this same process for web programmers. I could easily hire an excellent programmer, but if they don't understand HTML/CSS/JavaScript, they become a liability in building a quality web application. At that point, it doesn't matter how good of a programmer they are if they can't professionally implement the necessary features. These are necessary tools of the trade.