The null reference was invented by C.A.R. Hoare in 1965 as part of the Algol W language. Hoare later (2009) described his invention as a "billion-dollar mistake":[10][11]

[1] http://en.wikipedia.org/wiki/Null_pointer#Null_pointer

Where:

[10] http://qconlondon.com/london-2009/presentation/Null+Referenc...

[11] http://www.infoq.com/presentations/Null-References-The-Billi...

Yes, the same video I linked above.