Exactly. The claim isn't that ubeam is viable, it's that investors like a16z with competent technical staff are more than capable of doing back of the napkin ph

Exactly. The claim isn't that ubeam is viable, it's that investors like a16z with competent technical staff are more than capable of doing back of the napkin physics before investing, so there is surely more to the story here-- either the company tech can be argued to be viable with more non-public info, or the investors are aware of the impossibility of their current claims but decided to invest anyway.