I think it's just kind of a satirical thing. It's like people go to Starbucks for their daily coffee to relieve stress and what not, but by adding the vodka and Valium, it shows that the people who get these drinks are becoming sad and depressed with their daily [sub]urban lives. But the previous answer was correct in saying that it doesn't actually have anything to do with Starbucks - I think it's just kind of showing us what the world is coming to.

I'm not sure but I looked it up on google and from what I can tell it has nothing to do with starbucks.