Money & WorkFact
How a rumour can kill a healthy bank.
Because banks hold only a fraction of deposits as cash, a bank can become insolvent when many customers withdraw at once. The rumour alone is enough: whoever believes others will withdraw, withdraws first. In 2007, customers of Britain's Northern Rock queued for days, the first UK bank run in over 140 years. The bank was nationalised.
Useful: Deposit insurance exists mainly so that nobody has a reason to queue.
Source: de.wikipedia.org