Yo, I agree. Once in my office, I was in a rush and stood on a desk chair on wheels. Just for a second, I told myself. Yup, a split second. Chair went one way, my body flew in another. Knocked myself out for a few seconds, and had dizzy spells with blurred vision so bad I'd feel nauseous for 6-10 months, with decreasing frequency. It pays to be careful.