Warning - sending ETH to Bittrex is a smart contract invocation. Very bad customer experience. Details inside.

So here's what I found after a friend asked for help:

• When you ask for deposit address in Bittrex, what happens behind the scenes is that a new instance of smart contract is created just for you. Here are the creation events: https://etherscan.io/txs?a=0x6cace0528324a8afc2b157ceba3cdd2a27c4e21f

• When an unsuspecting user tries to transfer funds, the usual 21k gas limit is not enough and the transaction fails, consuming gas in process. OUCH!

• Looking at the list of contracts above (go to contract address via internal transactions), you can see it happens to oh-so-many people. I wonder how much customer support pressure it generates for Bittrex?

• I see transactions succeeding with around 22k: https://etherscan.io/tx/0xd89ef9721c0f1885cd115049d945b37b46114590f2adaaee2604cec8046dee99 https://etherscan.io/tx/0xc0cf52b96fd7f709415a3a931a3f6f13e974c21f2f21518a9417b557f4a7a4fa https://etherscan.io/tx/0xefc9ab9f957ae01b47d75672c16c49fa0a54ebc20e804776b3c5281711dc50df (all found randomly on the above list).

• I'm also seeing Bitfinex sometimes initiating "sweep" transactions on unfunded addresses: https://etherscan.io/tx/0x3a30fdf7146a8d09ca42c5de74a2ae37894f4373453243632af0ca38376d2df9 Thats 47k gas at 33 gwei gas price! Hey Bittrex, WTF are you doing, how much money is it wasting you?

tl/dr: increase gas limit to 50k when depositing to Bittrex. Bittrex, fix your shit.