You always own a copy of my wallet's private keys since without them you wouldn't even be able to read the addresses inside. What stops you from withdrawing all I have deposited in said wallet before disappearing? How will I be able to recover my wallet anyway if your whole site suddently goes *POOF*? I mean this is not a bad idea overall but obviously lacks a financial scheme of any sort. I don't think anyone with a basic understanding of how a ponzi works will ever deposit funds in your site. It's just too good to be explained with "one simple strategy: marketing". I deposit 1 BTC (currently 11.150 USD) and you give me free 0.0066 BTC (70 USD) every day? Come on... If you can explain where are you supposed to earn money to pay for thousands of user's interests I may as well decide to trust your site. Without this information I don't see why I can't simply tell you how much BTC I hold in my cold storage paper wallet and ask you to give me compound interest everyday for hodling it