Using market cap of AMZN and EBAY as proxy for B2C and C2C market, this is an interesting chart of their dynamics over last 10 years.  Obviously, this chart is in US dollar, and 1 US Dollar in 2001 worth more than 1 US Dollar in 2011 due to inflation, and this chart has reflected the inflation component.  Taking out inflation component, it shows that at the early Internet years, C2C market is bigger and peaked first, while B2C market catch up later on and exploded in exponential rate a few years after C2C market’s peak.