The question -- whether the company's tablet cannibalizes sales of its own portable computing line -- is ultimately impossible to answer, or at least quantify: One can't look into a counter-factual crystal ball to view an alternate universe without the iPad.

But Tim Cook, Apple's CEO, believes that the iPad does block sales of at least some Apple personal computers.

"I think there was some cannibalization from iPad," Cook acknowledged earlier this week during his company's quarterly earnings call with Wall Street.

Cook offered that view while answering a question about the poorer-than-expected sales of Apple's laptops, which were up just 2% over the same period the year before -- in line with the computer industry's overall average increase, according to IDC.

The 2% year-over-year increase in unit sales was significantly lower than Apple's laptop line usually garners: In the first quarter of 2011, for example. Apple sold 53% more notebooks than it did the year before.