What makes the world go 'round?

This is a fun one...

I've got a Boy Scout campfire song stuck in my head: It's cheese that makes the world go 'round. The song links together a chain of actors, where each makes the next "go 'round". So cheese makes the mice go 'round, which make the cats go 'round, and so on until we finish with the observation that "it's love that makes the world go 'round."

So what really makes the world go 'round? Tell me anything you think of--relating to economics, politics, society, etc. Here's a shot at what the campaign-finance reform crowd might say:

It's money that makes the ads go 'round
It's ads that make the votes go 'round
It's votes that make Congress go 'round

And then they can follow with a chorus like:

roll over for special interests, roll over for the rich

So, do you have any ideas? This stuff is modular, so we don't even need complete chains--we can link ideas together later. So what makes things "go 'round"?