It is reasonably closely related, since I think one of the most important functions of the blacklists is to warn people about transfers that might cause them to lose funds.

I've been considering a similar idea for a while for the wallet functionality. For the fiat money transmission sites I use, I have to first setup specific "beneficiary" accounts, and only then can I make transfers by selecting from such a list.

I think a similar function would be useful in the UI, such that when the user types an account name he has never sent to before, it would warn him that he has never sent to it before, and ask them if they want to do the transfer. This prompt could also ask if the user wants it to be added to a list of "commonly used" accounts that would show up as a dropdown below the edit box (which would be filtered as the user typed characters).