Funny thing: I typed in a complete paragraph from 'Breakfast of Champions' By Kurt Vonnegut and the computer said: "I write like Stephen King".
'Nuff said, fo sure.
EDIT: I think it's keyword based and doesn't mind style one bit.
If you enter some Getrude Stein crap (using metric schemes from her "Tender Buttons") that uses words from Douglas Adams' books, like so:
"The Captain drove a Ford and went stellar. Stellar Captain in a Ford. The universe was filled with life. Planets. The sun. The Captain drove a Ford in the universe.
What do you mean that the warp warp warp warp warp thingimajig doesn't do interstellar? In the restaurant at the end of the universe. Galaxy. Universe. Radius. Sun. Solar. The captain fucked Ford in the restaurant."
well, then your comp will say: "I write like Douglas Adams."
Similarly, this fragments says I write like James Joyce, because I'm just using some of his words:
"I fucked a chick in Dublin. On the ladder of life life was like a bloom, said Molly. Everything is full of Bloom, boom, boom. A hattrick for Dublin. Streets full of Irish melancholy. Insomnia for the meek. I am an artist and this is my portrait. Like the Greeks, like Leopold and Hades. The stare of a cyclops."
So yeah: Not impressed at all.
EDIT 2
If you enter a repetitive sequence like:
"fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck fuck [...]"
I write like William Gibson.
I add two words to this sequence: "portrait" + "artist"= I write like Chuck Palahniuk (I expected Joyce, though).
I add two words: "women" + "sexuality" = I write like David Foster Wallace
I add three words: "life" + "hell" + "eternity" = I write like Stephen King
Pffffffffffffffff... THere's a system in there, ad it's rotten like the state of Denmark.