I personally don't use big words, because, well, I sort dislike them; whatever I say comes naturally from my mind. If there's any word that you rarely see used, chances of you seeing me using it would be very unlikely. :] Only time I'd ever use them is when writing something that requires their usage, such as some form an important paper. I see a few people use complicated words here and there, and that kind of... annoys me, unfortunately, haha. Since I'm not very used to them, they make things harder for me to understand. I am able to figure out what they're trying to get across, but it takes more time than it actually should, which I don't really like.