ITT: Post your worst experience in dealing with crypto or trading crypto -- I'll go first...
Exactly one year ago, when one Ether was a mere $8~ or so, I decided I wanted to do a ShapeShift from ETH -> BTC.
Open up my wallet, paste in the proper address, hit send.
Waiting.... waiting... waiting more.. WTF? Shapeshift doesn't confirm receipt. Ethereum is always fast on ShapeShift and it never takes this long.
I take a look at the transaction details... mother of God. I had been researching other Ethereum tokens on Etherscan.io and had copied the MakerDai contract address to look at its code.
Apparently, I didn't copy the incoming address on Shapeshift and was too idiotic to confirm the address was correct.
FML.
Knowing that the MakerDai devs would be the only people that could possibly have the key for this address, I tried contacting Shapeshift support to see if they knew the devs or if they could do anything (they didn't and couldn't, of course).
I then found the Maker slack channel and quickly got in touch with the lead dev. He was exasperated and thought some noob had sent ETH to the contract trying to get tokens in return. Regardless, he informed me that the contract is completely separated from human intervention, barring a hard fork.
So, unless Vitalik and the ETH foundation feel like erasing this transaction ID from the blockchain in the event of their next hard fork, the Maker Dai contract will forever be enshrined with my stupidity.