A big chunk of the asset value is in listed stakes like Chinese e-commerce giant Alibaba and SoftBank's now separately traded telecoms unit. Yet the whole has been beaten down partly because investments by the company and its affiliated $100 billion Vision Fund in WeWork, Uber Technologies, India's Oyo and others are looking a lot less smart than they once did. A renegotiation of the merger between SoftBank-controlled Sprint and T-Mobile US is a risk, too.