It was very good marketing when you use your eventual earnings to lure in customers. Though, it's getting too popular now and people know it as a scam (or as good as one). So I think the better marketing choice now'adays is be realistic. Put how much money they generally can make in their first week (even if it's like $10-20) but in the advertisement thread/page you can put down the eventual earnings and supply proof. I think honesty, is now possibly the best marketing method for eBook sellers, and it's a method I welcome.