Assaf writes about, among other things, REST as a simplifier of development against an existing system:
REST plays the same role as open source and open APIs: It eliminates tooling and vendoring as artificial barriers to adoption.
As a result of building a website for a Torchbox client, I came up with a Drupal 5.x module to query the Postcode Anywhere and MailBuild webservices (if they look like an unlikely mix, don’t worry: they’re not coupled together generally, so you can use one without the other). I’ve been meaning to make it live for ages, but never got round to scrubbing the client’s data out of it. Now that we’ve unearthed the module for other work then I’ve finally finished cleaning it.