Ive lost about .3 BTC on bittrex when i had no 2FA installed (yeah i know...)
I think several accounts were hijacked by an apparent "hacker" who stole a lot of coins (i think
https://blockchain.info/address/1GMYnJQrUae7QzTcSVSAiGEHob6ewfHLr2 is the address) ... i emailed bittrex and they claimed they are investigating. After sending several emails requesting the ip address of that user who logged in for months i got absolute no reply until i had to threaten legal action and the next day i receive the ip address but no word on the investigation.
But like a goof, i continue to use bittrex for the same reason as most will use it now.
One time I left my iPhone in the car unlocked. It was stolen so I reported it to the police and demanded they match the fingerprints from the door handle to their database and give me the offender's name.
They said they were investigating but I figured because I showed so little care to start with they'd not investigate properly.
To this day, like a goof, I still call the police.