We're basically just talking about "rules of thumb" here. From Wyeast's website: "A rough rule of thumb is to double pitch rates above 1.065 and triple pitch rates above 1.085. Or, more technically, a million cells per milliliter are needed for a 20degree plato"
Pitching the "standard" rate of 0.75m/ml/*P for ales is as much a "rule of thumb" as what Wyeast recommends. There's no way the "standard" rate will give you the optimal fermentation in every type of beer.
Right, this is something that's good to mention. Even in brewing texts and the commercial world, pitching rates vary from place to place and style to style.
The Mr. Malty calculator assumes 0.75 million cells/ml/Plato for ales and twice that for lagers. Wyeast basically claims that because this is fresh, lab grown yeast and not harvested yeast from a previous batch, you can get away with less for low gravity ales. You can see that they recommend a lower pitching rate for beers under 1.060, while advocating using a higher rate closer to the commercial "standard" (if that truly exists) for high gravity beers. They also rationalize their lager recommendations based on warm pitching, which is a great way to make a fruity lager unless you really have the ability to cool the beer fast in the first few hours after pitching.http://www.wyeastlab.com/hb_pitchrates.cfm
Given that yeast is not always shipped in optimal conditions, and may be sitting around for a month before you get it, I'm not sure that it's really true that you can pitch less because the yeast is fresh. Homebrewers have had great success using Jamil's pitching rates.
I do think that Mr. Malty's yeast viability estimates are very pessimistic.