You have probably heard (or even said) at some point in your career that an average American is exposed to 3000-5000 ad messages every day. But do you know where this number comes from? If you do, please leave a comment. If you don't, you are not alone. Not having an idea either but very curious, I spent some time poking around. Take a look at my initial findings.
Update [Jan.28 '08]. President of Yankelovich, J. Walker Smith, sheds more light on the number's genesis in his comment on the Hill Holliday blog.