The Chinese eCommerce market was worth over RMB 4.5 trillion ($685 billion) in 2010

"The China B2B Research Center of e-commerce site Netsun Toocle (002095.SZ) has released its 2010 China E-Commerce Market Statistical Report, revealing that as of December 2010, China's e-commerce market value exceeded RMB 4.5 trln, up 22% YoY. B2B online transaction volume reached RMB 3.8 trln for 2010, up 15.8% YoY, while B2C/C2C transaction volume rose 97.3% YoY to reach RMB 513.1 bln.
The number of B2B e-commerce companies in China rose 21.3% YoY in 2010 to reach 9,200, with combined revenues up 35% YoY to reach RMB 9.55 bln. Alibaba held the largest market share with 63.5%, followed by Hong Kong-based Global Sources (Nasdaq: GSOL) with 5.3%, Made-in-China.com with 3.4%, Netsun Toocle with 2.9%, and HC International's (8292.HK) HC360 with 2.5%.
In 2010 the sector raised USD 550 mln in capital from 42 investors, including 35 VCs, as well as two IPOs that raised a combined USD 389 mln and five mergers.
China had 15,800 B2C/C2C firms in 2010, up 58.6% YoY, with the number expected to exceed 20,000 in 2011. Market share among China's C2C e-commerce platforms broke down as follows: Taobao, 85.4%; Tencent's (0700.HK) Paipai with 11%; Tom Eachnet with 3.1%; and Baidu-Rakuten, a B2C e-commerce joint venture between Chinese internet company Baidu (Nasdaq: BIDU) and Japanese e-commerce firm Rakuten, with 0.4% of the market."
Source:  Marbridge Daily, 21st January 2011
Note - I have assumed that 1 trillion = 1,000 billion (i.e. trillion has 12 zeroes), although in some countries trillion has 18 zeroes
Currency converted on Xe.com on 24th January 2011 - RMB 1 = USD 0.1519