What would be the effect on the demand on M2 if banks instituted overdraft protection

Even if you regularly peek at your bank balances online, it is possible to accidentally let your account fall negative, otherwise known as overdrawing your account. For example, you may have written a check to a company or individual who did not deposit it immediately. A debit card transaction may not have cleared quickly, and your balance was larger than it should have been. Or, a deposit could have been delayed, leaving you with insufficient funds to cover your withdrawals.