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...
That in theory should solve everything but even so, blockchain analysis will always be around. Maybe when coinjoin comes out it'll be a big business trying to figure out who's sending what where (and when).