source: http://www.businessweek.com/news/2014-04-11/bitcoin-mining-boom-sputters-as-prospectors-see-real-cash-losses
if they are mining 21,000 BTC a month it would make their farm just over 20% of the network.
This article is absolutely devastating for individual miners future. What is quite surprising to me is that, apart from Bitmain, no other manufacturer has ANY price flexibility whatsoever. This indicates that hardware suppliers simply choose to mine themselves when bitcoin prices are declining. Every manufacturer price was completely unrealistic in the last couple of weeks (KnC, cointerra, spondoolies, even Bitmain S2). I think that we are about to experience a hard crash in hardware manufacturers. I dream for a modular low power cheap machine. Some guy has S1 undervolted with less than half electricity consumption, but still decent hashing:
https://bitcointalk.org/index.php?topic=526060.20