"Dividing revenue by employee gives us a better look at which companies are the most efficient. And that’s what you see in the chart at the top of this post."

craigslist's numbers are misleading here. Sure, they're extremely efficient by the above metric, because they were lucky enough to become a de-facto standard marketplace. I challenge anybody to find another example of a software company with 30 employees that is nearly as successful.

MSFT revenue per employee is $631k, between eBay and Facebook.

Source: http://www.wolframalpha.com/input/?i=microsoft+revenue+/+num...

(PS. Do I deserve extra karma for posting this cool WolframAlpha link ? :)