The whole objective in assembling a business school class is to put together people who can share unique experiences from their industries.  If you have two years in your industry and another applicant has five years in the same business,Admission Officer will to take the more experienced candidate over you, even if his GMAT score is a little lower than yours.

But That Won't Happen to Me!

You think your 720 GMAT and 3.6 GPA will get you into Wharton.  After all, you have almost two years at Salomon.  But look at the numbers.  Only two percent of last year's class at Wharton had less than two years of full-time work experience.  That means 15 people out of 8,300 applicants (one of the highest acceptance rates out there).  That gives you a 1-in-553 chance.

The vast majority of inexperienced applicants get the ax and have to reapply the following year with a lame story about why they were rejected previously.

And, by the way, you don't get to apply from ground zero the year after you have been rejected.  At many schools all you are allowed to submit is an updated information form and a single essay explaining what has changed in your life since you last applied.  

What if I Changed Jobs?

The general opinion seems to be that changing jobs isn't a problem, especially if the change involves some kind of promotion.  But "job churning" is frowned upon because the admissions people want you to have more than just a surface understanding of your industry.  You need to bring a certain amount of expertise to the classroom, and changing jobs every six months will make it difficult to develop an in-depth understanding of a specific industry.