OK, RC5-56 was designed to prove how weak 56-bit encryption is.
RC5-64 merely proved how STRONG 64-bit encryption is, as far as the lay person is concerend.
So what will RC5-72 achieve?
It certainly won't convince anybody that 72-bit keys are easy to crack (even though 72-bit encryption is not particularly strong), so what's the point again?
Other than wasting a significant amount of electricity worldwide?
Seriously. If someone can give me a good coherent argument as to why the RC5-72 "competition" will server any benefit (other than having a minute chance of winning a grand), I'd be delighted to know!