APIv9 is now available at http://api.builtwith.com.

This new version includes 2 new properties on each lookup –
• IsDB – A true/false if this result came from the database or was a live lookup.
• Vertical – The vertical classification of the website based on IAB Tier 1 categories (like Business/Automotive/News etc..)
A new parameter (NOMETA) provides the ability to not return meta data, which will increase the performance of the API if you do not require this data.
See http://api.builtwith.com for more documentation.