Overheard [Financial Analysis and Commentary] What's old is new again, even on the stock market. People date themselves when they talk about developing actual rolls of film to see their snapshots. They might be even older if they reminisce about playing videogames at a shopping mall arcade that required tokens. Two companies that saw their heydays decades ago from now-antiquated products have embraced one of today's hottest new technologies: blockchain. Atari, the onetime king of videogames, is the latest.