Experts have warned of the perils of relying on a small number of companies for operating the global internet after a glitch at Amazon’s cloud computing service brought down apps and websites around the world.The affected platforms included Snapchat, Roblox, Signal and Duolingo as well as a host of Amazon-owned operations including its main retail site and the Ring doorbell company.More than 2,000 companies worldwide have been affected, according to Downdetector, a site that monitors internet ou...