How do classified sites like Craigslist make money?

How does Craigslist generate revenue when both posting and responding to listings is free? The only category they seem to charge for is the jobs section.

Is that enough of a revenue source for them to keep the service going?

Why wouldn't a site like Craigslist add Google AdSense ads and make far more money then that the jobs listings probably generate?

Craigslist main source of revenue is charging for listings in a few commercial categories:

• Jobs
• Apartments / real estate
• smaller categories like therapeutic services

Due to the tremendous scale of their traffic, charging for these categories seem to be enough of a revenue stream to keep them profitable all these years.

The reason they don't have display and text ads on their site is probably because of their core value of keeping the experience dead simple.

Craigslist generate revenue through the…

• Job listing –

1. $25 per ad for New York City, Los Angeles, San Diego, Boston, Seattle, Washington, D.C., Chicago, Philadelphia, Orange County (California) and Portland.
2. $75 for a job listing in the San Francisco area.
3. $10 fee to list an apartment rental in New York.

• Banner advertising or Google text ads

For further information go to - http://en.wikipedia.org/wiki/Craigslist