The main argument against the bitcoin price over at /r/buttcoin is that tether is the one pushing up the price by minting unbacked tethers and then buying bitcoin.
I personally think the price would have and will rise regardless of tether, so essentially if they are scamming then they are coming along for the ride and getting rich in the process.
So can someone explain what exactly is stopping tether just buying bitcoin with unbacked tethers? It seems like the perfect scam, mint tethers, buy bitcoin and then get rich as the price rises. Then when people try to redeem the tethers they will have the corresponding money to pay back the fake tether (they made it through their bitcoin profits). Rinse and repeat.
I personally don't think the current price is the result (or solely the result) of tether, as there is clearly massive demand. I also think if tether collapsed it would dent the price but not in a massively meaningful way.
EDIT: They would also have the motive; the 100,000 BTC hack that bitfinex had is just mind boggling, wouldn't be hard to imagine they they cooked up the idea of printing unbacmed tethers when thinking how to recover from the hack. What have they got to lose, they already lost big time …