Today, Amazon will start its fifth annual Prime Day , which has been expanded to 48 hours this year. Designed to enlist (and keep) Prime members, it is the company's biggest shopping event of the year -- on the same level as Black Friday -- with extensive discounts and deals across the entire site. At a time when Amazon would likely prefer that all its employees hunker down to meet increased demand, a group of warehouse workers in Shakopee, Minnesota are going on strike . It isn't the first time the workers in Shakopee have raised their concerns. But it will be the first major work stoppage event for Amazon in the US and could be a harbinger of things to come.