I gave a talk at Heroku's Waza conference this year, discussing moving from monolithic applications to service oriented architecture. My goal was to dispell the myth that SOAs are particularly complex or that they slow down development time for both scrambling startups and mature businesses. Neither are true, and starting with a simple appliation structure- simply starting with two applications, one serving a RESTful data API, and one to use the API and serve your front-end (be it web, mobile, or otherwise)- will, in most cases, increase your efficiency, increase the longevity of your code, and will allow you to scale in application complexity without sacrificing code quality or agility.

Check out the slides at http://vimeo.com/video/61043049.