In Manassas, WalMart is building a store in the site of an old Sears on the corner of Manassas Mall. They had to tear down the old Sears building, re-locate a stream, do all new parking, and then connect their building into the existing mall structure.
Maybe there are other places Walmart prefers to build virgin, but they obviously are willing to recycle as well.
My former hometown had a battle with Walmart. Walmart wanted to build on a farmer's field, but neighboring residents didn't want the additional run-off the new asphalt would cause as the area had already been prone to some minor flooding. After a protracted battle with Walmart, which was claiming that it was going to be the field or nowhere, Walmart eventually ended up tearing down an adjacent (and mostly abandoned) strip mall and built there.
Everyone eventually got what they wanted, but it was probably a little more expensive than what Walmart had hoped.