This is I think what happened, if you trace back you find that one person bought ~5 million BCY during the ICO in 2015.
2 million were recently moved to Poloniex as indri123 noticed, 1 million on the 28th, 1 million was moved time ago. So about 1 million BCY remain in the original address.
Even at current prices it's a lot of profit to be made from ICO prices so whoever that is they are cashing in and there's nothing anyone can do about it.

Here's the address: http://blockscan.com/address/14mrvfR6VajW8CA3u5d2LrQjKtb2oWifdm, follow the trail.

Just hope they run out of BCY soon!