We have been building over cemeteries for centuries.
While I believe most current cemeteries should be preserved for the sake of urban and suburban greenspace, I think there is good reason for us all to consider our plans regarding our own death. Continuing to take up the kind of space that existing cemeteries take up isn't sustainable.
That said, I live in an area with a lot of really cool pioneer cemeteries, filled with names anyone who studied the Oregon Trail would know (or anyone who played the game!). I'd like to see them preserved, as many of them are beautiful greenspaces, and of historical value.
My favorite cemetery in Oregon is the Old Scotch Church cemetery, off of Old Scotch Church Rd. n. of Hillsboro, Oregon. If you ever get a chance to visit it, do.
http://en.wikipedia.org/wiki/Old_Scotch_Church