There's a phrase at one of Chicago's hackerspaces (and probably at many others): Just Fucking Do It.

Talk is cheap. Implementation is hard (and more interesting); JFDI.

Naysayers will naysay, but a thing that's done is more powerful than "Oh, well, you can't do that because"; JFDI.

It also extends to telling people they don't need permission. If it won't be costly (in time or money) for other people to undo, you don't need to ask -- JFDI.

Hyperloop seems really weird, but arguing with Elon Musk forging ahead is weirder.