Food Delivered: Facebook Has Decided to Join the Fight

Facebook launches a food order and delivery service. 

One guy does it, and now, everyone wants to do it.

Who is in this food delivery service game already?  Amazon, Uber, Lyft, McDonald's, and etc.  It will be interesting who becomes the last man standing.  Let the fight begin.

How will Facebook's participation in the fight affect these players' stock prices?