Hello,
I buy Bitcoin locally with cash and charge a 3.5 percent commission. I then sell the Bitcoin in Kraken and cash out.
I've been noticing that some of the Bitcoins I get are tainted (
https://blockchain.info/taint/*bitcoin address here*) and I'd like to know what risks I'm taking by selling such Bitcoins there.
Should I be worried?
This brings us to the old bitcoin problem: lack of fungibility. Since the blockchain is public, some addresses have been linked to criminal activity. It shouldn't be a problem, because all bitcoins should be considered valid, but if authorities decide it's a problem, then it becomes a problem, unfortunately.
I hope future improvements in privacy such as CoinJoin and Confidential Transactions can be enabled by default and work seamlessly. Meanwhile yes, you should worry about coins linked to criminals...