This thread has the potential to become hilariously cringeworthy in a decade or so. I'll be checking back in five years to see if lightweight VTOL aircraft are still an idea that is "obviously stupid because we've tried it before and it didn't work".
My guess is that the progress in batteries and electric motors will have made this concept a lot more feasible by then. At some point it will be a completely obvious idea which will make us shake our heads at the skepticism it had before.
The problem isn't the tech. There have been flying cars--as in, vehicles that are both road- and airworthy--for more than half a century. The problem is the logistics and practicalities.
No, they do work just fine with Jet-A. Are they practical? No. Will electric battery technology overcome the constraints within 5 years? That's a viable hypothesis, sure.
I don't think battery technology could overcome the specific energy constraints in 5 years... Seems highly unlikely.
Jet-A is 46 MJ/kg -
Lithium Air ~40MJ/kg -
Lithium Ion is 0.85MJ/kg
Lithium Air is the only thing remotely feasible that 'functions' in a laboratory and it has not left the lab since 1970.
"Another recent review on Li-O2 batteries, authored by materials scientists from Technion- Israel Institute of Technology (Balaish, Kraytsberg et al. 2014), concludes with : 'The possibility of buying off the shelf Li–air batteries within 10–20 years does not seem realistic at the moment.'"
It wouldn't be an entirely apples-to-apples comparison to jet fuel. A fully-electric VTOL aircraft would ditch most of the wings, for instance, and instead make the fuselage lifting-body.
Wings are large to provide enough lift at takeoff and landing speeds, tail and rudders to provide aerodynamic stability which would be provided by electric motors instead. Also, the engines would be lighter and a significant fraction of the empty weight would be batteries. We wouldn't see an electric drop-in replacement for a long-distance airliner in the near future, no one is claiming that.
My guess is that the progress in batteries and electric motors will have made this concept a lot more feasible by then. At some point it will be a completely obvious idea which will make us shake our heads at the skepticism it had before.