The case, for anyone who is interested, I alluded to in my previous post is Berman v. Parker in 1954. Here the Court allowed DC to condemn slum--real slums, not like Kelo's house, areas with the eminent domain power. DC sold the land they condemned to private developers. So, there is the 'landmark' precedent in silly journalist speak (Lawrence v. Texas is the 'landmark' in this link if you have a slow connection like me and don't want to take it).
I think 'landmark' makes a good euphemism for bad decision or departure from the Constitution. The press cheers, "the Court is advancing our social causes, yippie! This'll be a landmark to guide judges in the future." And all along I thought the Constitution should be the judge's guide. Call me a reactionary...