I always throw a whirlfloc in the kettle and never had a problem making a hazy beer. I'm guessing some of the haze comes from yeast but I have noticed that some hops, such as Belma, add a TON of haze during a dry hop. Between the Whirlfloc and a trub dam, I have almost perfectly clear wort going into the fermenter but that doesn't mean it won't be a hazy looking mess going into the serving keg.