How big an impact, if any, does distinct IP subnet have?

[ChrisInColorado]

I have two customers that sell the same product.  Their content is logically similar because they are selling nearly the same thing.  The part numbers, descriptions, code base and underlying structure are different however.

One customer is complaining that because I host both of these sites in the same server cluster on the same subnet I am negatively affecting their ranking.

To what extent might this be true?  I've always held that unless the content is identical the subnet thing was just a myth.

Any opinions?

[KevinBudzynski]

Doesn't matter much anymore according to Matt Cutts.

[ChrisInColorado]

Nevermind - saw the link now....duh....