To be honest, these concepts were made multiple times before (BitMit, Coingig, Cryptothrift) but few succeeded because of the complexity of such system to run stable on 15000+ users.
I was learning about Bitcoin and came up with this idea myself, and then did research and I indeed concluded there were multiple attempts and sites that have this concept.

No idea was stolen, and everyone is free to work out ideas? Idea's can't be  patented or trademarked.