rate limiting

[jgn]

"All applications are subject to rate limiting. The rate limit is service-wide for the API as well as the website itself. The rate limit as of June 2008 is limiting to 3 messages sent per minute for a rolling 60 seconds. This limit is per user key, not per developer or app." (http://groups.google.com/group/pingfm-developers/web/api-documentation?_done=%2Fgroup%2Fpingfm-developers%3F)

It would be useful if this API had an option to measure request frequency, and provide the caller with a callback that might sleep appropriate. The callback would pass the recommended number of seconds to sleep.