Starting out with a dumb UI shouldn't be a problem as long as you are free to progress to greener pastures. It shouldn't be that you have to learn how to take apart a type writer before you can write a book, the technology doesn't require it.

A clear road beyond will also take down the walls around the silos since effort to control the user would come at a price (force them off the platform(s) faster)

We could perhaps start by separating the API from presentation? Have A scalable chunk of FOSS at first hosted by a megacorp but easily moved some place else and A presentation platform where people build their gui that is as easily moved.

(Just thinking out loud, didn't put much thought in it.)

edit: your own domain should be an obvious ingredient. Which seems to suggest that domains should be free?