We have to stop fooling ourselves, Bitcoin, by design, is not fungible. Some already use this, some will do. Sadly, against us.
Bitcoin is fungible as long as people act like it is. If you treat Bitcoin as if it's not fungible, you risk that the payment you receive today becomes worthless tomorrow when you find out the previous owner had stolen it. Treating Bitcoin as if it's not fungible seems to be the most successful attack on Bitcoin so far.
1
BTC=1
BTC. The end.