I am not sure exactly how they are doing it, but there is certainly no random generator at work here. I have carried out an experiment - using the first chapter of some books I have on my phone and from literature.org the following matches were made:
Nicolas Nickleby by Charles Dickens, "I write like Charles Dickens".
Impressive, thinks I. Lets try:
Emma by Jane Austin, " I write like Charles Dickens". Well, you know, there actually is some truth in that in terms of sentence structure and grammar.
What about:
A Scandal in Bohemia, by Arthur Conan Doyle. But I changes the name Sherlock Homes to Jim McGill and Irene Adler to Jessica Adams, juut yo reduce the chance of some skulldiggery.
" I write like Arthur Conan Doyle"
Hmmm.
Crime and Punishment by Fyodor Dostoevsky. Used the second paragraph because the place names in the first paragraph are in a distinctive structure. " I write like Charles Dickens". Not as clear as with the Austin, buyt still, probably not a bad comparison.
Alice in Wonderland by Lewis Carroll. Name Alice changed to Jimbob.
"I write like Lewis Carroll".
And then I got bored.
Quite an impressive strike rate - I wonder what samples it uses for comparison and how many authors it has on its database, but it looks pretty good on this sample.
Oh, and this post, right up to the wors "sample" above - "I write like HP Lovecraft.

"I mean, if everyone had a soul, there would be no contrast by which we could appreciate it. For giving us this perspective, we thank you." - Nate
"I write like..."
26/10/2010 12:13:04 AM
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...I put in a steampunky fantasy story I've been playing with and got H.P. Lovecraft.
26/10/2010 01:35:15 AM
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Stephanie Myer, Bram Stoker, Stephen King and Cory Doctorow
26/10/2010 02:00:40 AM
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That is because it is a random generator...
26/10/2010 03:17:02 AM
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It sounds like they have a limited list of writers to choose from as well.
27/10/2010 01:13:10 AM
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Dan Brown, Charles Dickens, James Fenimore Cooper, Ursula Le Guin, and Arthur Clarke...
26/10/2010 03:26:28 AM
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Cory Doctorow, whoever that is *NM*
26/10/2010 10:10:23 AM
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Down and Out in the Magic Kingdom
26/10/2010 04:25:56 PM
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and then read Little Brother.
26/10/2010 04:29:11 PM
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Oh, interesting! Genre? *NM*
26/10/2010 08:30:21 PM
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That really is awesome! And it is definitely not random...
26/10/2010 04:23:36 PM
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Goethe's Faustus returned Pj Wodehouse *NM*
27/10/2010 01:21:29 AM
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Corey Feldman?
26/10/2010 05:15:58 PM
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Did you submit the script for the third Lost Boys movie? *NM*
27/10/2010 02:04:16 AM
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Nope. Dream A Little Dream 3. *NM*
27/10/2010 06:48:57 PM
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It's funny, I almost made a Dream a Little Dream joke instead of a Lost Boys one. *NM*
27/10/2010 11:18:07 PM
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I did two tests on two different chapters of one of my stories on ff.net...
26/10/2010 10:35:36 PM
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I write like H.P. Lovecraft and Margaret Atwood. *NM*
26/10/2010 11:17:53 PM
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That was with very recent pieces. Older ones got me J.K. Rowling and Chuck Palahniuk. *NM*
26/10/2010 11:21:22 PM
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Douglas Adams, that might actually be valid, he's the first fiction author I read, on the other hand
27/10/2010 01:13:45 PM
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