I think web developers need to have great people skills. Getting project requirements from a client is a difficult task, as well as being able to translate the technology jargon into something your client will understand.
Web developers also have to really keep up with the latest technologies, and not be too comfortable in one area. The web is constantly changing, and we need to evolve as well. ;)
I'm mostly a PHP Lamp developer, but as new technologies are introduced, I'm trying to find time to learn ajax, best user interfaces practices, SEO, and much, much more.