it's not a marketing problem. people outside a given field will, by virtue of their inexperience, be prone to more hubristic ideas they don't understand the impossibility of. combined w/ the tech scene's natural credulity - as demonstrated by the Soylent debacle - & there you go.
the problem w/ casually describing it as a "marketing problem" is it completely excuses both entrepreneurial excess & the whole Valley hype thing. sure, there should be an onus on people to present/market their ideas well, but also on the public to be a little more skeptical of wild & unfounded claims.