Eminent Domain Explainer?

I'd love it if one of you lawyers could please explain today's Eminent Domain ruling to me, a lowly engineer.  I don't understand this thing politically at all.  Why would the "liberal" bloc vote for this thing? It seems to me that this ruling will reward big-money insiders at the expense of the average Joe.  Shouldn't Democrats be on the side of the average working family? I realize that court issues are different, but you would think that they'd have at least the correct inclination.

I just can't believe I'm agreeing with Thomas and Scalia on this.  What am I missing?