(By the way, neither do we believe that brick-and-mortar is dying because of e-commerce. Sears, like many other struggling retailers, was a victim as much of good old-fashioned poor management and an inability to embrace omnichannel strategies as anything else.)

Many malls around the country have responded brilliantly to this new-age challenge, and operators have awakened to the value-add of gym members finishing their workout and browsing the variety of retail venues at their disposal. It's all part of a major industry push to create more of a mall “experience” (to use a much-overworked retail phrase) with a proliferation of restaurants, movie theaters, and other venues not traditionally thought of as mall fare.

In fact, one source puts the increase in mall-based fitness centers at 70 percent over the past seven years. So the closing of Sears's stores provides a perfect dovetail for this gym expansion.

For net lease investors, the now vacated spaces of Sears and K-marts, which number close to 300 around the country, will be unique assets.  Most are not owned by the mall, but rather by Sears' parent holding company.

This provides an interesting opportunity in many of these locations for a single-tenant net lease investment, providing attractive long-term rental rates and built-in traffic patterns. So if you're an investor in STNL, keep your eye on shuttered Sears and Kmart stores. A door might be opening for new net lease inventory.

The views expressed here are the author's own and not that of ALM's Real Estate Media Group.