I agree with Blandry - to be considered anything more that an averagely good developer more is needed that knowledge about your subject area. There is a need for a wider appreciation of how things work together - different technologies, front, middle and back end, etc... decisions should be taken based on 'this is the best tool for the job' rather than 'this is the tool I know hence it will be better than everything else'.

In my experience, far too many developers think they are great because they know the .Net framework inside out, or know c++ inside out but have absolutely no knowledge (or indeed wish to have any) of the technologies for the back end, how they work, how to use them, which are best suited for what, etc. Technology is moving too fast to only know one side of it!