Perhaps someone is confident that they can have your wallet.dat at will and is trying to 'launder' value through your identity. That would be a method I might employ if I had need to cover my tracks. (I would probably leave you with your initial balance since I am not a thief...though it could be argued that using your existence in this way would be a form of theft.)
Note that this is a _hypothesis_ and nothing more. Many people get confused on the meaning of that word.
^^^ This. That was my gut feeling. Anybody who is able to generate that quantity of BTC at current difficulty is smart enough to know they're not receiving their deposits... so either you have a Great Expectations anonymous benefactor (Spoiler Alert: It was the convict he gave vittles!), or someone is about to rob you. I'd generate a new wallet, move the coins, change your passwords everywhere, etc. and do some serious spyware scanning.
Worst case scenario, you're being paranoid, but have raised your security and technical knowledge in the process.
If not, PLEASE don't come crying in here about how all your BTC were stolen.
Best of luck!
