We recently made changes to our pricing structure and as a result, our API rate limit is changing tomorrow, August 22, 2013. Previously, we had an hourly limit of 600 requests per hour for each nation. As nations grew, we realized that this wasn't providing a consistent level of functionality across nations. A small nation could accomplish almost anything, and a large nation could not accomplish even a small goal in a timely manner.
We will continue to throttle access on a per-nation basis, but the limit will be enforced on a daily basis, instead of hourly. To fill the second-to-second rate limiting needs of our infrastructure, we will now have an additional rate limit on requests made from the same IP address of 250 requests per 10 second interval. For more information, see our updated rate limit policy: http://nationbuilder.com/rate_limit_policy.
If you have any questions about these changes or our API, contact NationBuilder Platform Director Arion Hardison at firstname.lastname@example.org.