What impact could it have on virtual marketplace companies such as Uber, Postmates, or Grubhub?

Case 2 Opinion Letter from Acting Administrator: U.S. Department of Labor

Assume for discussion purposes that the company being evaluated in this letter is Uber and the question is whether its drivers are independent contractors or employees. Do you agree with the analysis by the Department of Labor that the drivers would not be employees?
Why is it important for the Department of Labor to publish an opinion on this topic? What impact could it have on virtual marketplace companies such as Uber, Postmates, or Grubhub?

What variables would need to change in the relationship between the client and the company for the DOL to consider the clients to be employees?