Article continues below advertisementThe disappearance of Nancy Guthrie has gripped the internet, transforming a deeply personal tragedy into a viral true-crime spectacle as amateur sleuths race to crack the case in real time.The 84-year-old mother of Today show host Savannah Guthrie vanished the night of January 31 near Tucson, Ariz., and was reported missing the following day when she failed to appear at church. Weeks later, with no suspects identified, the case has drawn massive online attention and mounting concern about the consequences of that attention.