Exactly. I'd add to that the introduction of dust or debris into the physical system. If a stick or leaf or bit of tinfoil wrapper got in between battery balls,

Exactly. I'd add to that the introduction of dust or debris into the physical system. If a stick or leaf or bit of tinfoil wrapper got in between battery balls, they could disrupt the connection or, worse, short the connection and create a fire hazard. Also, any physical recycling/reclamation system has two disadvantages 1) capital investment in "balls" by the vendor (larger than just investment in a static power station) and 2) theft/vandalism prevention i.e. you've got prevent users swapping fake, damaged or substandard "balls" for good ones. Image a gang of ball thieves swapping 3D-printed balls filled with clay for good ones and reselling them. Or, imagine terrorists/vandals introducing fake balls filled w/ fireworks to destroy your charging stations or (if clever enough to pass as real) redistribute balls to sabotage unsuspecting cars.