Skyler Bartels kept looking over his shoulder. It's a habit he picked up living at the Windsor Heights Wal-Mart for three days. Really living there. Eating, sleeping, checking out the DVDs, never leaving. The plan was to spend his entire spring break there. Under the radar. Some kids go to Cancun. Skyler Bartels, a Drake University sophomore from Harvard, Neb., went to the garden and patio department. The great experiment had been over for a few days, but Bartels was still in great-experiment mode. As we sat at a booth in the Subway sandwich shop toward the front of the...