In a lofty address that at times resembled a campaign speech, the chief executive of Wal-Mart Stores, H. Lee Scott, said that “we live in a time when people are losing confidence in the ability of government to solve problems.” But Wal-Mart, he said, “does not wait for someone else to solve problems.” Mr. Horowitz said Wal-Mart had room to improve, however. Its next goal, he said, should be to stop selling the least energy-efficient products, rather than simply introducing better models.