You can't short BTC/USD from bittrex and Poloniex,
Thanks for the correction. My account application at Poloniex is permanently stuck in verification and I only have basic verification at Bittrex hence I use Bitfinex for 99% of my trading.
also CME opens future markets, shorting at a future market won't require you to "lend" any bitcoins, which makes it totally different.
I really don't see that this makes a difference. Mainly I say that as the introduction of futures didn't have a negative effect on any other assets when they were introduced. There are plenty of Bitcoins available to borrow on Bitfinex and I don't see that market leading the others when there is a fall in price.
Until now the big whales has made their profits from eating small fishes on the uptrends( buying low and selling higher), but now they can earn massive from the opposite.
Again experience from other markets suggests this doesn't impact prices. We have seen time and time again when markets have crashed and regulators have banned short selling as a kneejerk reaction that it has failed. After an initial pop when those already short were forced to cover the market then resumed going down at the same rate it was before.
Also the futures market on CME is planned to have a massive liquidity, a lot of people who thinks that bitcoin is a bubble would be able to easily short it.
The CME can't plan liquidity it just depends on how many traders turn up. I'll certainly be there as the advantages of trading futures with the extra leverage, reduced costs and a professional execution platform will make it the best place to trade.
This. But the CME only allows them to short futures - if the underlying asset (bitcoin) performs well, all that will happen is that the shorters lose money.
Spot on. Futures contracts are deliverable so there will be plenty of people wanting to buy the futures if they were trading lower than the spot markets.
The whole thing is really a matter of opinion and I'm basing mine on my views on futures and the effects of shorting on other markets. You'll find plenty of people on both sides of the argument on the trading forums as well.