So at least according to the "a company is worth X years of future earnings" model, Apple is priced as a company that will grow even less than IBM and Microsoft over the next X years. Or perhaps it's priced to grow a bit more in the immediate future, but to start declining after that.
There are certainly other factors at play as well, but I don't know them well enough to enumerate them.
My main point was simply that when you think of "present company value" as the integral (the area under the graph) of the earnings graph far into the future, and add growth rates and fluctuating uncertainty, several non-intuitive aspects of company pricing start to make more sense. Even if it doesn't explain everything.
Apple has had a few quarters where year-over-year growth was around 100% (last in Q1 2011), that hasn't been the case in the last few quarters.
The market may be overreacting, but given that investors look at graphs like this and try to project the growth trajectory from the past few quarters several years into the future, pricing Apple a bit below Microsoft in terms of P/E doesn't seem all that unreasonable.