> Seemed like there was some circular or backwards reasoning, like that Apple's potential future growth makes its past growth likely to continue, or that Apple's cash increases the stock's value even if you ignore its cash.

Apple's cash position projects power.

This is what fundie investors who subtract cash aren't factoring in. The ability to make strategic buying purchases which constrain supply for competitors is not easily calculated.

Here is their latest (publicly known) deal with Samsung: http://online.wsj.com/article/BT-CO-20110213-704284.html

Now think about the "ability to make such deals" with valuations 10x that... Can Dell, HTC or RIM do this? If not, then they are at a disadvantage, as Apple could massively out-bid them on volume with key suppliers.