Not sure why this is being down-voted as it is essentially true.

Large banks do have bugs, and sometimes even admit it. [0][1]

The fractional reserve system basically means if there is a problem, you need to be the first at the counter. If you are not, you will only get a certain amount of money back.

[0] http://www.telegraph.co.uk/finance/2737388/Bug-crunches-Hali...

[1] http://www.independent.co.uk/news/uk/home-news/lloyds-bankin...

Edit to add: (But not quite the same as the one above)

http://www.dailymail.co.uk/news/article-2426519/Gang-arreste...

http://article.wn.com/view/2012/06/26/Lloyds_TSB_computer_gl...