People (usually) don't hire based on specific skillsets. They hire for talent and passion, and figure that if someone really wants to be working on that problem, they'll find a way to teach themselves what the need to know.

My last job had two main projects - a Netbeans plugin and a JSF webapp. I had no JSF and no Netbeans experience, though I'd done Java Swing development before and written several PHP or Perl webapps. My coworker on the JSF project was a former COM and .NET developer who didn't know Java.