Anil Dash, in "Crossing the Threshold", succinctly captures something that had been kicking around in my head:
Web-based writing tools tend to be the opposite of desktop writing tools in the sense that the tools form around the ways people write, instead of the desktop application model, where the tool informs and influences the works that are created with it.
MovableType is what FrontPage should have been.
I'll add a minor contribution to this train of thought. Eventually the ways people read and write with Web tools will filter back to the desktop. For example, RSS aggregators got a kick start be having HTTP/HTML frontends (cf Radio Userland, AmphetaDesk). Now desktop versions are coming back with a vengeance (cf NetNewsWire, FeedDemon).
A thesis. Web development is so constrained that it forces developers to have a clear data model and be on task regarding the task.
Also, Web development really supports rapid, iterative prototyping. Granted, hitting reload isn't as much fun as a Common Lisp REPL, but it beats compile/link/debug.
I wonder if there are any companies out there working with a "prototype on the Web/deliver on the desktop" model. Strikes me as a possible winner.
And another nugget. If you believe Dash, bake extensibility into your app from the get go. This allows the tool to adapt to how people write. That may seem obvious, but you'd be surprised how many young developers have to be convinced that extensibility is a good idea.