An analyst at IHS Screen Digest has estimated Steam's 2010 revenue at "high hundreds of millions of dollars," while Gabe Newell has said the company is "tremendously profitable".
Valve is remarkably tight-lipped about Steam's financials, but a profile on founder Gabe Newell has rounded up some interesting snippets.
According to Forbes, Valve still employs only 250 staff, and "per employee" is allegedly more profitable than Apple or Google. The company is valued at at $2-$4 billion.
Steam's user-base of 30 million is the largest in the industry after the big three - Microsoft, Nintendo and Sony.
It's also the largest in the PC gaming sector. Last year the NPD revealed digital distribution passed boxed sales, and of that $4 billion market, Steam is said to hold "half to 70 percent".