how is "job experience" of a candidate evaluated?

I have heard people saying that B-schools are inclined to a certain type of sector and pay less heed to the experience, lets say, in IT sector. Is it true? And also, what is the optimum job-ex? some say 2 years. How BIG a deal is this job-ex! ::

I have heard people saying that B-schools are inclined to a certain type of sector and pay less heed to the experience, lets say, in IT sector. Is it true?
And also, what is the optimum job-ex? some say 2 years. How BIG a deal is this job-ex!