Last night on public TV's "The News Hour", they interviewed some of the homeowners affected by this sort of condemnation proceedings. In one place in Ohio, condemnation was used to provide land for private development using a clause in their condemnation/eminent domain laws that allows condemnation if the area is question is "blighted". The definition of blighted and it's application was evidently highly subjective as the houses shown in the news clip were older, well kept small homes that in this area would be considered normal well kept middle class housing.
I think railroads being able to use eminent domain, is a fairly unique special case. No railroad could have been or could be built in the future without this ability in most cases. There are a lot of cases back in the old days where small towns and individuals tried to extort more money from a rr than what the land in question was worth. It's kinda funny when rr's ended up bypassing certain towns that tried this.