Craigslist

http://www.wired.com/entertainment/theweb/magazine/17-09/ff_craigslist?currentPage=all

The battle flows back and forth. Captchas—distorted words that can be interpreted by humans more easily than by machines—tamed spam on craigslist for a while. Then it came back full force, not because the spammers had solved the difficult problem in artificial intelligence but because they had hacked an easier problem in global economics. I recently established a friendly email dialog with a young man in Dhaka, Bangladesh, who works on a 13-person team that creates craigslist spam. He fills in Captchas, creates new accounts with masked IP addresses, and posts ads all day long using text from a database provided by his employer, an anonymous spam king. The going price for a spam post on craigslist is about 50 cents, with large discounts for volume. When I told Buckmaster about my new friend, he took the news calmly. "These are technically sophisticated people who take pride in their work, and when we knock them down they don't just decide to go find something else to do. You could say we are breeding the perfect spammer."