If you are a web developer, chances are you've already built a REST API. But not all of your customers can program. With Zapier, your users can put your API to use in thousands of unique ways.
If you are a hacker, maybe your favorite site doesn't offer your most missed feature. With a few flicks of the wrist you can add a custom service to Zapier and hook it into any of our existing services.
If you are an in-house developer, you probably build lots of internal services, but even those need to talk to external services like Basecamp or Mailchimp. Adding a JSON API for Zapier gives you thousands of integrations at once.
Just like our customers, chances are you won't even need to write a single line of code! (Though you can, if you want.)