If you are a site owner and are looking for people to join up on your forum. One way that i found that works very well is giving away cash prizes or something.
Like one forum i go to the most referals (has to be over 50) Wins an ipod touch! Well in that month they gained over 6k of users. (4.5k where legit)
So ya. If you have forum money form advertisements buy some stuff and give it away.
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