Calcruzer, i will be attending Wharton next year.
in the last few months i've talked to a lot of people who will be going to school with me next year. yes, a number of them have had business extracurriculars. however, there is a fair number who have not. personally, i have never taken a course in business or economics, and i have never done anything directly business related (except work in my dad's small business during the summer, which wasn't one of my top 6 activities anyway). i'm not just an exception, because I know plenty of other people who got in without business extracurriculars.
yes, i will agree with you that they look for leadership. however, the organization that you lead is not your sole qualifer to be a leader in business. some people took the lead in business-related clubs or started their own companies, and other people (like myself) found opportunities in other clubs and organizations. you should still have a strong interest in business or you'll have a miserable time at wharton. for instance, i love reading the wsj and business books. however, its important to just find something you are passionate about and excel there.
here's a quote from the dean of admissions that touches upon the subject( first question on page 2): http://www.businessweek.com/bschools...ams_getting+in