When a Weibo user publishes a post containing link to an individual product page on Taobao, this module will be inserted right below that post showing related product information. Other users will be able to click and find out more details on Taobao.
Top 10 downstream websites on Sina Weibo represent 27.2% of the total, among which Taobao took 8.2% (source: Sina Weibo annual report 2012). So, it makes sense Sina capitalize on this with this partnership. It’s probably charged on a commission model based on referred traffic or sales; and, the details is not disclosed at the moment.