There has been a request to be able to withdraw BTC through the API at bitfloor. Since our goal is to provide a robust, documented, and fast API which meets trading needs, we have added this feature.
It is documented on the REST api documentation page:
https://bitfloor.com/docs/api/rest#send-fundsPlease let me know (email to support is best) if you experience any issues with this new API. It is available on testnet and production as of today.