It would make life interesting for multistorey car parks. It's not uncommon to have 500+ spaces. If each one of those has something between 3-50kW charge capacity, and many are being used at once, that's going to require some serious infrastructure upgrading (maxes out at ~25MW if I didn't flub the numbers). A wild ass guess would put them in the maybe-hundreds of kW for lighting, ventilation, automation, so that's a pretty big step.
Then again, they'd be in a pretty good position to monitor spaces used and already have a billing system for parking time, adding cost of power would be quite straightforward.
And it's going to be a long time before 100% electric occupancy is a real problem.
It's sort of a microcosm of the problem of upgrading the grid to handle the additional load from charging EVs. Like the grid, I think it will happen so gradually that it will barely be noticeable, and the upgrades will just be a part of regular electrical work.
Note that you'd only need to size for average use, not peak use. With a bit of cleverness (and expense) you could set a power limit for the whole garage and distribute it between the charging cars, rather than letting everyone charge full blast. Most people will drive under 50 miles per day on average and will charge overnight, so you really only need to deliver about 1.5kW per car. (50 miles at 300Wh/mile is 15kWh, assume "overnight" is ten hours of charging.) You'd want to be able to provide more for those who need it, but that's probably a reasonable number for an average.
I have 10kW charging at home for my Model S and it's major overkill for local driving. Most public chargers are about 6kW, which would still be plenty for daily charging.
Tesla already has a lot of technology in their Super Charger stations to control the total charge rate. E.g. if you park right next to another car both will charge slower, because there is a limit in power per 2 adjacent parking spots. The same goes for the total over all spots, if they are all in use, the cars will charge slower.
So having 500 spots in a garage means you'll need to have some technology that is aware of which car is in need of charging and when the owner is expected to return. You can then set dynamic pricing to motivate car owners to charge at the moment you have enough capacity and encourage them not to all request full charge-rate at busy moments in the garage.
Just in case some Tesla owner discovers this fact here, a seriously tiny nitpick: supercharger pairs aren't necessarily directly adjacent. Your best bet is to look at the label. 1A is paired with 1B, 2A with 2B, etc.
In any case, allocating power between cars is relatively easy. The cars themselves can be told how much they're allowed to draw, and this can be changed on the fly, so you don't need any fancy power electronics, just enough smarts to monitor usage and tell cars how much they can take based on that.
