Fulfillment centers can come in all sizes, ranging from the behemoth centers larger than a million square feet to 200,000-square foot regional centers to smaller 50,000-square foot buildings, which might have 20,000 square feet dedicated to e-commerce. Most online retailers are in a big hurry in choosing a facility, which often rules out a build-to-suit option.

“They have a need for speed,” Conklin says. “A lot of these guys don't have time to wait. There's plenty of good, high quality spec buildings available and not many at all are looking at build-to-suit.”

The need to be close to population centers in order to provide quick service to customers will push investment into infill situations, panelists agreed. “Infill locations near major markets will be the winners,” says Nick Firth, SVP, acquisitions, LaSalle Investment Management.

During a question and answer session, panelists noted that not many facilities are being developed on brownfield sites. Rakusin says he knows of projects in Baltimore and Bethlehem, PA, where large tracts are being reorganized for e-commerce. Conklin says his company has worked on redevelopment of an old Boeing site in Seattle for a build-to-suite project for Amazon.

The debate of the e-commerce promise was the subject of another panel. Demands for faster delivery of goods are putting pressure on retailers. Bryan Jensen, principal of St. Onge Company, a supply chain consultancy, says these demands are requiring more automation.

He noted that robots can replace some labor, but they can't do everything.

Ben Conwell, former director of real estate with Amazon, says the old trend of building huge distribution centers far away from major metropolitan areas is clearly waning. He notes that Amazon's Prime Now service, which offers one-hour delivery in Manhattan, will drive a new real estate model of 30,000-square-foot inner city fulfillment centers.