That's obviously not true, since the ranking produce and reinforce reputation even at the regional level. Compare the average salaries of the schools. Numbers 31-100 have higher average salaries than number 101 to 200.

I think it's beneficial to think of these rankings in terms of "tiers" - that is, tier one is the top 30, tier 2 goes to 100, and tier 3 would be schools that aren't ranked but accredited. You can compare schools within the same tier, but for most situations comparisons between the tiers don't really work.

Another caveat: In the US, you'll find that the top-tier schools usually have dedicated full-time MBA programs, while the lower-ranked schools are more likely to mix part-timers and full-timers (in general). Mixing students isn't a terrible thing for the most part, but for many students, having a dedicated full-time cohort can be a more immersive experience. Also, the top tier schools will have substantially better career services capabilities than other schools.

Like most things in life, there is no simple answer. Surveys show that the number one factor in choosing a business school is reputation and image. There is no single more influential measurement of reputation and image than a ranking.

Still, it?s important to remember that there are no perfect measurement systems to determine the best schools. The methodology behind every ranking?whether BusinessWeek, U.S. News & World Report, The Wall Street Journal, the Financial Times, or The Economist?has inherent flaws built into them. So you need to know what a ranking is actually measuring and whether those measured attributes even matter to you. (See our detailed examination of the strengths and weaknesses of the key MBA rankings.)

Found this article best for this: http://poetsandquants.com/2010/06/28/do-mba-rankings-really-matter/