Yes, they do, and I've seen it once or twice on here from blog posts from company leads/founders talking about their applicants. I don't have it handy, because

Yes, they do, and I've seen it once or twice on here from blog posts from company leads/founders talking about their applicants. I don't have it handy, because I don't bookmark that sort of thing, but they believed that you could overdress. They're simply looking for someone who doesn't dress up because they believe that will indicate someone that they'd want to hire. You, as the applicant, may not be aware of this because there's often incomplete information on both sides of the table (that's what the interview is for). You can always ask indirectly, stop by their place and peek through the windows, or research this information yourself, like looking at company photos. Or you can just do what I do and dress up anyway because someone who believes that dressing up is a negative mark is probably not compatible with me.