I tested this a while ago by auto-generating websites with millions of keywords. Surprisingly, I was able to get the websites ranked for many long tail keywords

I tested this a while ago by auto-generating websites with millions of keywords. Surprisingly, I was able to get the websites ranked for many long tail keywords and it started to bring over 100,000 visitors per day. Though it didn't last very long, Google penalized the websites after couple months. I did it for testing, but it could be an effective strategy for spammers who could rinse, repeat and scale. There are many websites like that still ranking and generating traffic; some of them have Alexa rank below 1000.