Poon joined the company only in July 2010 and was charged with guiding Mediabrands Ventures' rapid expansion in the country and overseeing the China divisions of The Lab and Greenhaus.
Poon has had more than 15 years' experience in the advertising and marketing industry in Greater China. Prior to Mediabrands Ventures, he was managing director of Puca Mobile, where he re-purposed the China division as a mobile media consultancy.
He also spent seven years as regional managing director for Tribal DDB, working with global companies such as HSBC, Audi, Microsoft and HP.
No replacement has been appointed.