Even in California, which limits Kelo-style eminent domain actions to "blighted areas", what constitutes blight is often what the government says. And often, it can be created where no blight exists, if the government is willing to spend some time creating it.
Case in point in Los Angeles: For over 20 years, the City of Los Angeles wanted to widen Overland Avenue between Palms and Venice Blvds from one lane each way to two-plus-centerlane. They had a 20-foot easement on property on both sides of the street. But the city didn't want to pay for the land. So, they began refusing any and all permits on the Overland properties unless the owners ceded the easement to the city -- almost 20% of each lot. This went on for 20 years. The only thing the city would allow was a zoning downgrade to light commerical.
In those 20 years, the properties went from single-family houses to crappy commerical conversions, with their values plumetting (or failing to rise with the red-hot West LA market). At the end it was 3rd rate auto body shops, futon sales, used car lots and at least one momentary crack house. A mini-mall and McDonald's were allowed, once they ceded the easement. By the time the city actually wdened the road, using eminent domain, the "just compensation" for the property was a fraction of its original value. This is apparently not unique.