This referral bonus have one limitation members can't offer some money for joining and make minimum 30 post if anyone do it it can't be counted !
Well, I don't think it's a limitation or something, because for just joining the referrer will not get anything. The referral has to make 30 posts, and any referral won't accept less than $1 for 30 posts, but the referral bonus is just $0.25 or $0.50 so I don't think it's a big issue.