I am interested to find out how and what exact method he used. As i noticed Adsense earnings seems to drop off day by day. But as long as you have a good legit whitehat traffic then you have nothing to worry but maintaining it would be the difficult part if you have some other ways of earning aside from adsense but if your focus on adsense alone then good and bad. Good as focus. Bad as worse whenever it will come a time that adsense will hit your account from being banned.