A group of Portland State masters of urban planning students just wrapped up a cool study of unimproved roads in SE Portland's Woodstock neighborhood. I first heard about their "Roadway Not Improved" project back in the winter when they applied for a Portland STOCK art grant—they didn't get the grant, but the five fledgling planners still put together a good website of their study and an interesting final report (pdf).
What the group found is that, with the city's "laissez-faire" attitude toward unimproved streets, neighbors have often overtaken the unpaved right-of-ways for their own private uses. With the belief that the unpaved streets will remain neglected forever, people have turned the roads into gardens, parking lots and extensions of backyards. Partly for that reason, a strong contingent of neighbors wouldn't want the city to swoop in and fix up the streets even if cost was no object.
The miles of unpaved roads is one of the many issues neighbors and politicians point out as an example of Portland's neglect of its neighborhoods to the east, so it's interesting to see that some neighbors prefer the personal reclamation of public space the power vacuum allows.