John Locke says: Honor parking-space lawn chairs!
Digging a parking place out of maybe 400 cubic feet of snow exerts a classic claim of property rights as described by John Locke. When somebody takes the trouble to create something useful out of a wilderness or a desert, Locke said, he obtains a natural right to use it for his own benefit to the exclusion of others.
I'm with Locke here. If you can't assume you'll be able to use the parking space you dug out, your incentive to create it would plunge. The city and neighborhoods would lose the labor of thousands of car owners who help recreate civilization each time the heavens dump white stuff all over the place. True, during the time the proprietor claims exclusive rights to the parking space by protecting it with a lawn chair, it's not doing much good for anybody else. But it does help society a little by furnishing "positive externalities," in the jargon. Cleared curbs make it easier to cross streets. Mail deliverers can get around more easily.
And in the long run, space-by-space citizen snow removal accomplishes what would be difficult for the city to do. Municipal plows can't clear curbs with all the cars parked there -- or even one or two per block. So by giving Baltimoreans temporary, exclusive use of the spaces they dig out -- allowing cars to move and commerce to resume -- civic good is accomplished. Honor those lawn chairs!!