Pixazza is a Google Ventures-backed photo tagging service that has been compared to an “AdSense for Images”.

Pixazza allows publishers to identify, tag and match products found within online images on their sites and then link them back to the inventories of Pixazza’s network of advertisers.

The service, which can be integrated in a site by adding a single line of code, allows consumers to browse the photos featured on a site and mouse over it to reveal information and pricing about similar products, and if desired, click to purchase.

How it works
Consumers simply mouse of over an image posted on their favorite website and information appears to provide more detail or enable a purchase. With a move of their mouse, consumers can get the look, the details and information about what is inside an image.

As of March 2011, the number of publishers in the Pixazza network has grown by 15 times, and Pixazza now enables images at a rate of 20 billion image views per year (Similar to the way that page views are used to measure web site traffic, Pixazza tracks image views, which count the number of times a web publisher serves a Pixazza-enabled image).