Let's say a .NET programmer works at a company which provides software on demand, not as a product. The programmer works in WPF for a period of time and he/she invests lots of time in it. He/she get very good at WPF and Windows Forms and desktop development in general.

But the company has to provide a web application now, so the developer has to learn MVC or Web Forms. He/she is not experienced in web development so he/she starts investing time in this new technology and in time they get good at it. But this time the company has to provide a Sharepoint solution, and so on.

What is more important:

• Being very very good at a certain technology,

• Or be as versatile as possible knowing less in each technology but covering a greater area of expertise?

Should the programmer keep studying and working in WPF until he/she reaches a guru level or is it a good thing that they had to learn other technologies as well?

I agree with those of you who will say that when learning different technologies you will also learn things which are useful no matter the technology you're programming in. But eventually, when the programmer will want to change jobs, will it matter more that he/she knows some WPF, MVC or Sharepoint than the fact that he/she is insanely good at one of them?

I would think the second one is more important since most companies are looking for a developer for a certain technology. I don't think there are many companies looking for technical know-it-all people.

What do you think?