[brlewis]

Benson's patent was for a particular algorithm, not an abstract concept, yet it was found invalid: http://en.wikipedia.org/wiki/Gottschalk_v._Benson

The RSA patent didn't make it through the patent system by claiming a particular algorithm; it made it through by including the hardware: http://en.wikipedia.org/wiki/RSA_(algorithm)

See also http://en.wikipedia.org/wiki/Freeman-Walter-Abele_Test