Detroit enforces its city building codes and will give tickets and court dates to these offenders, Winters says. Of course, it's up to the neighbors who are still around to let the city know.

This grassroots redevelopment should not take the place of large-scale city redevelopment planning or the marketing of prime parcels for more tax-contributing dense developments along major transportation corridors, planners say.

Cleveland, for example, has held back some of its more marketable lots to try to attract more commercial and mixed-use occupants near light rail, says Lilah Zautner, sustainability manager with Cleveland's nonprofit planning partner, Neighborhood Progress.

Of course the sale of these residential lots in most cities does not preclude them from being sold down the line or divided up again, as the zoning on them does not change, planning officials say.

Changing the urban footprint?
It remains to be seen just how much of an impact blotting will have on the urban landscape in cities such as Detroit, Cleveland and New Orleans. Right now, these big lots make up just a small fraction of the tens of thousands of vacant lots the cities own in these areas. Many blighted sections of these cities are so filled with apartments and renters that there's not enough vacant land, or non-landlord owners, to create blots.

Time will tell just how much blots bring up property values in the areas where this expansion has been allowed. Harris looks at it this way: "You can actually sell a house now on this street."

What's clear is that many of the city planning departments that once dug in their heels over these purchases are now working to encourage them. They see it as an option to save their budgets and make their city more livable for the short term, even if it means community gardens and basketball courts rather than businesses

Cleveland, for one, is even reaching out to existing homeowners to let them know the option is available, Zautner says. After all, Cleveland has 20,000 vacant lots to fill in the years ahead — 8,000 of which are held in its land bank.

Who knows? Maybe decades from now, homebuyers in some of these cities might look closer to downtown to find a bigger yard.

"If enough of this blotting goes on … you can really de-densify the city," says Dan D'Oca, a partner of Amborst's at Interboro. "In some ways, it would be great if the city was more like the suburbs. It's just creating more housing choice."