eminent domain : evil or benign?

I had a good conversational debate with a neighbor this morning on the issue of eminent domain. As I left the house and crossed the street, I noticed a new sign our neighbors across the street had posted. Tacked to a tree in their front yard, the sign read "We want a sidewalk and bike lanes. Place sidewalk here" with an arrow pointed down to the base of the tree (about 7 feet into their current property). The issue was therefore on my mind when I arrived at the bus stop at about the same time as the other neighbor.

A bit of context before I go into our debate: Hanshaw Road has an active sign culture. A fellow on the corner of Hanshaw and Warren changes his handpainted signs, which present political viewpoints and quotations, on a regular basis. He's fought for the right to post these signs on his property, when challenged by neighbors. Two houses down from me, the woman on the corner of Hanshaw and Blackstone frequently posts political signs and anti-fracking posters. Over the past few weeks, new, professionally produced signs have cropped up all along Hanshaw. Some read "We Want the Walk!" and others "Say No to Eminent Domain on Hanshaw." The residents along Hanshaw Road generally do not shy away from public discourse. The city's plan--to put in a sidewalk on the northern side of Hanshaw Road, and widen and pave the shoulders to make them negotiable for bicyclists--has created a rift between neighbors.