Say what you want, but Macromedia Dreamweaver came pretty close to being "that killer app". Microsoft attempted the same with Frontpage, but abandoned it pretty quickly as they always do.

I think that Web Browsers need to change what they are. They need to be able to understand content, correlate it, and distribute it. If a Browser sees itself not as a consuming app, but as a _contributing_ and _seeding_ app, it could influence the semantic web pretty quickly, and make it much more awesome.

Beaker Browser came pretty close to that idea (but it was abandoned, too).

Humans won't give a damn about hand-written semantic code, so you need to make the tools better that produce that code.