A bad guy somehow gets your Online user name and password.  What can he do while he’s there?  The more controls you have in place, the less that bad guy (or gal) can do to hurt you.

Of course you must balance the relative safety of disabling access against your convenience in doing what you want to do with your accounts.

Imagine if you put a different lock on every door in your house and locked them all, all of the time.  Even if a burglar managed to get in your front door, he would be thwarted every time he tried to go into one of the rooms.  However, it would make living in your house very inconvenient for you and your family.

So you weigh these two extremes and come up with something in the middle.  On your house, you make the front door very difficult to enter, and you put your valuables in a safe with a combination lock.  Online, you set up controls that make it difficult for someone other than you to log in, then you put extra locks in place by deactivating certain features or requiring a second password wherever you want extra protection.