I've seen a few movie reviews of World War Z saying that a true adaptation wouldn't work, or at least wouldn't work in a film setting. I don't believe that.
Assume, for the moment that the movie is going to be 2 hours long (give or take), which is pretty standard, minus credits/title sequence. Also assume that every story in the book could be broken down into 5 to 10 minute long short films (with some time for the interviewer sections), with one or two parts being longer.
Here's how you do a World War Z movie:
Part 1 -- Warnings:
1. Do the Chinese section (where the infection started)
2. Possibly do the Brazil organ story (but not necessarily needed)
3. Do the Israel story (where Israel builds a wall), and possibly combine with the Palestine story
(10-15 minutes, give or take)
Part 2 -- Blame:
1. Do the "Wacko" story and the Grover Carlson story (show initial response of America)
2. Do the Montana story also (might not be needed, but could introduce the Phalanx stuff)
Part 3 -- The Great Panic:
1. Do the India, Barbados, and first Denver, Colorado bits. Possibly do the Russian story, but not entirely needed. The Denver bits take up more time, due to their complexity
(25 minutes, give or take, possibly 30)
Part 4 -- Turning the Tide:
1. Do the Redeker plan stuff (South Africa), and possibly the Canada story
(10 to 20 minutes, depending on Canada story)
Part 5 -- Home Front USA:
1. Do New Mexico (Arthur Sinclair), the 2nd Wacko story, and possibly the Malibu story, but not needed
(10 to 20 minutes)
Part 6 -- Around the World and Above:
1. Federated States of Micronesia (Radio Free Earth)
(let's say 30 minutes for all 4? These could probably be trimmed up a bit)
Part 7 -- Total War:
1. Denver Colorado Pt. 2
3. Denver Colorado Pt. 3
(Quebec isn't needed, per se, but both Denver stories are critical, let's say 30 minutes, but only 25 for just Denver 2 and 3)
Part 8 -- Goodbyes
3-5 minutes of everyone in the story giving their conclusion speech.
Total run time? On the conservative side, 125 minutes, or 2 hours and 5 minutes (that's with every low value assumed). Possibly 130, with interviewer parts included. If you assume a longer running time it's 160 minutes or 2 hours and 40 minutes. That time might be a tad long, but certainly doable (look at the Hobbit or Dark Knight Rises for examples).
So, YES, World War Z (as written) could be adapted just fine into a movie. Brad Pitt just wanted a passion project and in doing so, has ruined a perfectly good book.