I can't think of anything legal that would net you 7% a week in a remotely safe manner. He has been going for a while now and only recently reduced his interest rates, so it may go on until there aren't enough new people signing up anymore.

I got in before the spike last summer and sold on the way down, netting some free hardware and USD, so I put what was left from that in. Worst case, I lose money that I earned through luck. Best case, new computer hardware!