> There's a reason Starbucks invests so heavily in their store's furniture and ambience: customers who spend more time there buy not only more coffee, but more food as well.

I'm not sure that's a 100% logical conclusion. Would one interpret that to mean that the ~50 people who spend all day sitting in the chairs generates more revenue than the many hundreds of take out customers that pass through each day? Sure, perhaps they make more revenue per individual person, but if you look at revenue per customer type per unit of time, the sit down in store customers are by far the worst revenue source.

I don't deny there's a reason they choose to have attractive interiors, but I doubt it is to encourage individuals to spend an entire day there, so Starbucks can reap the windfall of selling the same customer breakfast AND lunch.