From Justice Thomas's dissent (thanks to Will for pulling the quote):
The consequences of today's decision are not difficult to predict, and promise to be harmful. So-called "urban renewal" programs provide some compensation for the properties they take, but no compensation is possible for the subjective value of these lands to the individuals displaced and the indignity inflicted by uprooting them from their homes.But this is America -- of course compensation is possible. My first inclination is to agree with Mithras and others who see this expansion of the takings doctrine as problematic only because there's a practical problem with computing appropriate compensation. If you're not repelled by the idea of takings in the first place (which I'm certainly not), then you have to see at least some logic in this decision. And the compensation problem, while significant, has to be exactly the same here as it would be if you were building a highway, since individual property owners in that situation are equally able to chaotically misrepresent the value of property to them in order to extort higher compensation.
The problem though, for me at least, is that businesses that stand to gain can bring a lot more political power (ie money) to bear on the situation, because they can spend against a promise of what may be massive future profits, which may end up distorting the public interest involved. In my mind this distortion effect is almost symmetrical with the compensation extortion the property owners can engage in, and the changes after Kelo will seriously disrupt that balance of power.
MORE: Nathan Newman's argument for the Kelo decision strikes me as a little condescending, but at the same time you could probably argue that poorer owners (or even non-owners) have a more difficult collective action problem to overcome because their own interest is relatively smaller. In that case though I think I'd rather see more protections for the poorer owners rather than none all around.
Also, I should have mentioned before that this isn't meant as a legal interpretation at all, since I know nothing about the relevant law; I'm thinking about this purely from a policy persepctive.
MORE: Will has more on the problems with fair market value compensation.