I'm trying to think of examples of technologies that were innovative and basically worked, but weren't potent enough to overcome the skepticism eventually, and/or couldn't overcome the deadweight of externalities. 

Not potent enough: flying cars
Couldn't overcome externalities: nuclear rockets

Any others?

Blogger at ribbonfarm.com, running summerofprotocols.com, host of /gloom ☀️

Complexity explorer. Residing in the liminal.

I think it's the energy equation that stops it from being economically viable -- it takes more energy to make and transport liquid hydrogen than it provides. So maybe it's a failure of the whole tech chain than just the cells themselves.

Is that failed or simply not yet technologically viable at a meaningful scale?