Last year I signed up for Pottermore beta, and was able to get sorted before the website opened to the public. Much to my pleasure, I was sorted into Slytherin, which is my favourite house (followed by Ravenclaw). That surprised me a whole lot, since some of the answers I gave seemed (to me) more like something a Hufflepuff would say. But since there are only about seven questions in the sorting quiz, and the combination is different whenever you answer it, I decided I would sign up and get sorted again when Pottermore finally opened to the public.
Well, just the other day, it did. And since I have three email addresses, I signed up twice more. The questions I got in the sorting quizzes were mostly different each time, but with a few common questions. The first time, I answered the questions like a Hufflepuff again, and again, got sorted into Slytherin. The second time, I answered the questions like (I think) a Ravenclaw, and was tied between Ravenclaw and Slytherin (the last question was just choosing between the two houses).
I also did the wand quiz two more times (obviously, since you have to), and both times, I got wands with a dragon heartstring core. The same core I got the first time. According to JK Rowling, owners of wands with dragon cores are easily swayed to the dark side. Therefore, according to JK Rowling, I should be a Slytherin who is easily swayed to the dark side. How stereotypical.