sorted file takes much longer to load

I downloaded the file of 5,000,000 supposedly hacked gmail addresses (from http://rghost.net/57937836). I noticed something odd with vim:

$ time vim -u NONE google_5000000.txt -c q

real 0m3.212s
user 0m2.971s
sys 0m0.232s
$ sort google_5000000.txt -o g2.txt
$ time vim -u NONE g2.txt -c q

real 0m54.808s
user 0m54.379s
sys 0m0.392s

Why should the sorted file take 17 times longer to load?

Regards, John Little

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