Locked Out of Your Account After Three Tries. It Makes No Sense.

Here's a scenario that no doubt sounds familiar. You type in a password to get into one of your accounts. The first two times, you type in the wrong password. Then you remember the right one. But your finger slips as you type it. You're locked out. The "three times lockout" rule is almost universally applied. It's also almost universally reviled. And to make things even more annoying: No one really knows why three is the magic number.