Web Designer = front-end only
Web Developer = back-end (i.e. ASP.NET, Ruby, PHP etc type coding), but also the talented guys can do front-end (web design) work as well.
No point calling a web developer a "software developer" either, because they ain't. Web development is one of the easiest forms of software development. Regardless of which framework you choose, they all provide a nice guided path that is "on rails" per se. At least compared to traditional software development.
That's a bit of a sweeping statement, don't you agree? The majority of applications are web-based these days. Intranets are fast replacing desktop apps for a number of things, yet still carry all the complexity of their predecessors, and more.
Starting to sound like a Dinosaur NathanE

I certainly agree there are many, many 'developers' that can manage a few modificaions to a CMS and not much more though.
it takes up so much time for our TL's to sift through the CV's and do initial phone interviews.