That you can't cancel a transaction you have made. I have lost money bcs of that, and that was the day that I realize that btc has disadvantages. I know that I had to be very careful, but we are humans and we do mistakes bcs we are tired etc. But foe me that's the biggest disadvantages of bitcoin.
Well that's a thing that should be a concern. Because when they could not do a deal with right then great loss will always be obtained. For every transaction we do in bitcoin can be small possibility to cancel, because the system in the bitcoin system does not recognize cancellations unless the people we invite to Transact want to understand or refund that has already delivered then it can be undone. So, this is indeed a bitch but if you look good then the system helps you to stay focused