response 1 of 52:

Mar 25 04:41 UTC 1992

The same number it would take if they weren't cut up into one inch squares.

response 3 of 52:

Mar 25 19:18 UTC 1992

It's debatable whether the result should be termed a pillow
if you didn't cut them up.  Unless, perhaps, you are into blocky sorts
of pillows composed of shifting rectangular parallelopipeds.  In
any case, you've identified an invariant property of the solution,
and that's progress.  Nice work!

Good responses so far.  You're getting warm.  Keep those wits and
pencils sharp!

response 5 of 52:

Mar 25 21:09 UTC 1992

If you shredded the paper into virtually paper fuzz, you could fill 
many pillows from one phonebook, and they would be fluffy.
The shredding tactic is what is used to make toilet paper "softer", in 
a lot of cases. They shred it a little, and it fluffs up. If you shake
the fluffy toilet papers (before using), little bits of paper will form
a cloud.

response 7 of 52:

Mar 26 04:03 UTC 1992

Re #4:  GOOD QUESTION!

Keep up the good work!

response 9 of 52:

Mar 26 10:05 UTC 1992

Good question!  You're getting warmer.

response 11 of 52:

Mar 26 14:08 UTC 1992

Congrats to Glenda!!  She got the correct answer, which is:

        IT DEPENDS.

Good puzzle-solving, all!

response 13 of 52:

Mar 28 04:34 UTC 1992

        You'd probably win any pillow fight you entered as well.

        I'd say the answer, "It depends", is lacking in something.  It
implies that there's only one variable, which isn't true.  It depends on
the size of the pillow case, and whether it has any holes greater than 1
inch.  It depends on how quickly a hole develops, on how many holes
develop, and how quickly they grow.  It depends on the composition of the
pillowcase.  If it's stainless steel, for example, it wouldn't take as long
to fill it as if it were made of silk.  And if it's made of plutonium, or
kryptonite, it depends on who you are, whether you can fill it at all.
        It depends on the form, as well...  if it's a Klein bottle pillow,
you can't fill it.  Unless you're God, or M. C. Escher. 
        Not to mention the composition of the phone book.  Make it floppy
disks, or bubble memory chips, and it takes more or less phone books,
depending.
        Naturally, no one will suggest the possibility of using only the 'Z'
pages, or not using the yellow pages, or the covers.
        The answer, 'it depends', is not as useful as it could be; once
you've decided what it depends on, you've opened up so many other
possibilities to consider.
        I suggest that this question cannot be answered at all, as there are
an infinite number of points to consider before you proceed to the
definitive answer.

response 15 of 52:

Mar 30 20:48 UTC 1992

That would depend.

response 17 of 52:

Apr 1 17:40 UTC 1992

It's not a problem; it's a solution!  (And who's this "John" person?)

response 19 of 52:

Apr 2 01:47 UTC 1992

Depends! For those let yourself go days.

response 21 of 52:

Jun 3 02:21 UTC 1994

Would it matter?
Why would anyone want to sleep on phone
books in the first place?

Besides that, I think the answer is 0.
Marston didn't ask us to stuff the pillow
case, he asked us to stuff the pillow,
which I'll assume is already stuffed
with whatever they use to stuff pillows.
(I don't think it's shredded phone
books, in any case.)

response 23 of 52:

Jun 3 10:21 UTC 1994

Actually, it wouldn't matter how many phone books you have to
stuff the pillow.  Phone books don't have arms or legs.  How could
they open the pillow?  How could they keep it from running away?