On December 3rd, I announced on twitter-api-announce that the Search API rate limit response code would change to HTTP 400 as of December 16th, 2009. (http://bit.ly/6yIjEn)
Based on feedback we've been getting, we won't be changing the response code for rate limiting to 400. For technical reasons, this code will have to change soon. We're considering feedback we've received to figure what makes the most sense. We will be announcing the change to another 400-series error code when it is apparent what is best. Thanks, Wilhelm Bierbaum Twitter Platform Team
