This is the first I've heard of this.

I'm surprised there is not already an incentive for recruiting. It did bring in a lot of people for Tsu (until it died) and some people made a lot from it. I still found that a lot of people would join and then do nothing or just try to spam to earn. I think these sort of sites need a good education programme to guide new users on how to proceed. I already see a lot of new users just voting and not posting. They don't have enough SP to earn that way, but probably don't realise that.