(copied verbatim from Pro ASP.NET MVC 2 Framework)
There are certainly cases where Web Forms is at least as good as, and probably better than, MVC. The obvious example is small, intranet-type applications that are largely about binding grids directly to database tables or stepping users through a wizard. Since you don't need to worry about the bandwidth issues that come with ViewState, don't need to be concerned with search engine optimization, and aren't bothered about unit testing or long-term maintenance, Web Forms' drag-and-drop development strengths outweigh its weaknesses.
On the other hand, if you're writing applications for the public Internet, or larger intranet applications (e.g., more than a few person-month's work), you'll be aiming for fast download speeds and cross-browser compatibility, built with higher-quality, well-architected code suitable for automated testing, in which case MVC will deliver significant advantages for you.