Would you want to know if those 7000 coins were coming from the addresses that are part of the BTER heist before you made the purchase or not???
If you say you don't care, then I think you are not being a responsible member of society. You should care and you it is easy to check, so why not do it.
I spend cash money at the grocery store all the time. Never have they asked for the source of the cash, nor my identity, for buying groceries.
Legally in the USA, you are not required to report a cash transaction to the government unless it exceeds $10,000.