"It is not all that uncommon in the investment banking business for a client to walk away from a trade.
Failing to settle a securities transaction on settlement day is known as "D.K." within the industry. The term is a contraction of "Don't Know."
The typical "D.K." occurs when a speculator or trade enters into a transaction for himself or for a client and refuses to settle the trade as agreed.
A "D.K.d" trade is typically associated with a losing trade.
In other words someone is trying to ride the bull market to new highs, and the market corrects itself downward. The long position the trader has placed has loses on settlement day, and they attempt to walk away from it.
Conversely, a trader that is short a position in a bear market (who anticipates the market going down and settling the trade by buying the security at a lower price than they sold it.) would lose money if the market rallied up in prices.
In both of these cases an unscrupulous trader may "D.K." the trade because it has losses in the trade that they either don't want to take, are unable to take, or unaware of the fact that a trade has been made in their name.
Never until the 9/11 put options, have I heard of anyone "D.K.ing" a trade that had millions of dollars of profits in it.
"D.K.ing" this trade is obviously a violation of security laws, but to walk away and leave millions on the table is because the person who made the trade know it is criminal blood money."
Does it matter? Seems to me that it might, but I'm not sure how.