have the most revenues of online companies, but it is almost without a doubt the most profitable relative to size. They have the highest revenues per employee of any blue chip company in the the tech industry.
But a lot of that revenue comes from sex ads, and in particular listings for prostitution, which are illegal in the US and many countries.
The New York Times has a story estimating Craigslist's sex-related revenue to be around $36 million dollars, or something close to a third of its estimated $100+ million in revenues. A lot of these are legitimate, but a lot are related to prostitution, and some to underage prostitution. So obviously Craigslist is being investigated yet again over this revenue. The fact that the company is fiercely private about its revenues and organization doesn't make the picture any easier.