To an extent, yes -- the current infrastructure is already over-provisioned by a factor of 2. (Each charger has two ports; if one car is plugged in it goes at full speed, if both are plugged in they get half. Each station has 4 parking spots, so that you can move the charging cord over to the next car when you're done charging your car.)

But when we start talking about "every parking spot" scale, then two constraints come to mind: (1) the charging rate is too low to be effective (L1 charging over "regular" 110V wall outlets gets you only a few miles of charge an hour), and (2) if you have too much current going through some common section of cable, it will blow a circuit breaker, or worse, overheat and cause an electrical fire (same as if you plug too many things into an extension cord at home or work).

Edit: I think the current state of the art for sharing is "push notification to tell the driver to move their car" because there is a non-trivial capital outlay for chargers even if you have enough electricity. So any scheme that involves all the cars being plugged in and some intelligent switching of who should go first still requires considerable capital costs, even before you get to upgrading the big transmission wires.

in the case of the office park, it's probably fine for the cars to charge at a reduced rate, as long as everyone has enough juice to get home at the end of the day.

in the case of a general purpose parking garage, this is less okay. I don't want to park in a garage for an hour to shop and not know whether my car will be at 30% or 80% charge when I get back. this is barely better than not having charging infrastructure at all.