So with simple classifieds without any advertisements and a .org domain name, Craigslist has been brilliant enough to fool the common man  that it is a non-profit site.  You will learn that it is a for profit business if you dig through their FAQ.    But what most of the people don't know is that the job listings they actually see are paid posts and in some cities real estate posts as well.  Still not convinced that Craigslist is corporate?  How about their latest lawsuits with eBay?  If you are still not convinced then lets take a quick look at Wikipedia's Craigslist page.
According to this page "The company does not formally disclose financial or ownership information. Analysts and commentators have reported varying figures for its annual revenue, ranging from $10 million in 2004, $20 million in 2005, and $25 million in 2006 to possibly $150 million in 2007. It is believed to be owned principally by Newmark, Buckmaster, and eBay (the three board members). eBay owns approximately 25%, and Newmark is believed to own the largest stake."  Not bad for a company with only 25 employees.
Sure, the simplicity of Craigslist may make you feel like comparing Newmark with Gandhi or Mother Teresa.  But the truth is that the latter two gave up everything for their cause.  But Mr. Newmark is milking it big.  Even Facebook is not making this kind of profit.
Moral of the story:  Learn how to screw the consumer ;)