Tesla is now facing its most dangerous adversary yet, and it could be proof that buying SolarCity wa

Walmart claims in a new lawsuit that Tesla was negligent in operating and managing 244 solar-roof contracts it had with the retailer. Walmart's complaint said Tesla's negligence resulted in fires in at least seven cases. Those fires resulted in store closings and millions in lost merchandise. It's likely that none of this would have happened if Tesla hadn't acquired the solar-services company SolarCity, which some critics said was a mistake in the first place. Now, Tesla is facing its most...