I think we need more categories: design, sys admin and security.
I recently need some security and optimisation help with a VPS host (still do actually - running VPSs to isolate websites from back end server), I looked on WW and there are no categories for systems administration. It is not a core webmaster skill in the way HTML is, but I am sure a lot of people here are good sysadmins, and a lot of us sometimes need help with it, and we need to find people we can trust not to mess it up.
The next thing I looked for was a web designer. Not a developer, a designer. There is are HTML and CSS categories, but that may mean technical knowledge of HTML and CSS. What I wanted was someone who is a designer who does HTML and CSS, rather than an HTML and CSS guru who can design - the primary skill is different. It needs a separate category.