Lingua Franca

I was just in line behind a guy at the airport buying a coffee, and this poor guy clearly didn't speak Starbucks:

<Barista>What size, sir?
<Guy>Uh, better make it big... uh.. GRANDE!
<Elliot>Uh, you know Grande is only medium, right?
<Guy>What? Really? No, stop.. Put that cup down, give me the Tall one
<Elliot>Seriously, Tall means small. You gotta learn the language man.
<Guy>What? That doesn't even make sense? What's big? Venti! Give me a Venti.

I thought the world learned this skill years ago. Maybe he was in a coma.

Then again, I'm pretty sure his drink was a decaf something-or-other, so that could be the problem right there.