Articles you read that claim they have 100 billion (or whatever) in cash are seriously confused about how cash and cash equivalents work.
From their latest 10k:
Cash and cash equivalents $ 10,746
Short-term marketable securities $ 18,383
Long-term marketable securities $ 92,122
(this is in millions)
Long term marketable securities are basically those things that they would likely take a significant hit on if they had to actually convert to cash in a reasonable period of time.
So how does this really compare to other companies?
Let's look at google.
As of September 30, 2012, Google had:
Cash and cash equivalents: $ 16,260
Short term marketable securities:$ 29,464
Whoops. It turns out google has more actual cash than apple, and more combined short term securities + cash. Just not as much in long term investment securities.
In short: Apple doesn't really have some amazing amount of cash.