The Bystander Effect

Description
When there is an emergency, the more bystanders there are, the less likely it is that any of them will actually help.
Pluralistic ignorance is where they assume nothing is wrong because nobody else looks concerned.
Bystanders go through a five-step process, during each of which they can decide to do nothing.

Notice the event (or in a hurry and not notice).
Realize the emergency (or assume that as others are not acting, it is not an emergency).
Assume responsibility (or assume that others will do this).
Know what to do (or not)
Act (or worry about danger, legislation, embarrassment, etc.)

Example
A famous case occurred in the early 1960, where Kitty Genovese was attacked and eventually murdered over a 45 minute period during which 38 people witnessed the attack and did not lift a finger to help in any way.
This was caused partially by social proof, whereby when people are uncertain, they look to other people as to what to do. It can also be caused by people losing themselves in the crowd and assuming a smaller share of the responsibility, expecting others to help in their stead.

MY INCIDENT

I actually found a loophole in the bystander effect. That is: If you have the knowledge of bystander effect, you would not let it happen!!!
I was in the bus today and a lady stepped in and asked everyone if they have change for a dollar. Everyone either looked indifferent to that or was looking at other ppl. Now, out of 10 ppl wat r the chances no one would have 4 quarters? (Stat students - calculate it!)I knew what was happening.. in the end the woman would have to put the dollar in the fare box instead of 50 cents because no one would respond. The "bystander effect" was taking place right infront of me. But you see, i already HAD knowledge of it... so wat would u do if u have knowledge of it? U would ACT! I said "yeah i might have it" (change for a dollar) coz i really did have it.

(You can tell this is a PSYC student talking!)