Speaking as a web developer, a designer who knows his/her way around a little web-speak is invaluable. I suppose this could be said of any medium that you are working in, that there are technological implications that a designer should always be aware of.

As a print designer, you need to know how a printing process works so you have an understanding of what happens after you hand off your files. As a web designer, knowing how your design transforms into code can make the transition much easier on both sides.