Snip from Poloniex terms:
"We reserve the right to restrict or refuse to permit withdrawals from your Account if (i) your Account has otherwise been suspended or closed by Poloniex in accordance with this Agreement; (ii) to do so would be prohibited by law or a court order or we have determined that the Digital Assets were obtained fraudulently; or (iii) you have not undergone the required identity verification procedure such that your identity has been verified, as indicated by your Account.
You can check whether or not your Account has been verified by reviewing your verification status under the My Profile section of your Account.
Upon closure or suspension of your Account, you authorize Poloniex to cancel or suspend pending transactions."
They are saying they will restrict your ability to withdraw if you deposit stolen money, laundered money, or have a court order to not allow you access to the money, or very similar. They don't have the ability to not process withdrawals for arbitrary reasons as is happening with LiveCoin.
Further:
edit: How about this, you can send 0.15BTC to 3P1o6BafmQomjKjakbK4ske8Lq8hCkJhiU to "speculate on the price of" 10 ETH -- I will not allow you to ever receive this ETH but you can sell this right to "speculate on the price" of ETH to anyone else who is a willing buyer. In my specific case, I am not scamming because I am disclosing your inability to receive ETH ahead of time, but LiveCoin did not do this, and as such is scamming.