Personally, I don't think we need to panic about anything. Think about it this way. If you get a degree from any top school (top 5, 10, 20, 30, 50), you are probably a very resourceful person who is multi-dimensional, ambitious, flexible, easy to get along, and curious (doesn't apply to *everyone*, I know, but just go along with me.

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During your 2 year in b-school, you'll meet hundreds of people to form your network and dozens of people to call your friends. These people will be from multiple industries, not just your own (even though you will probably have slightly more friends in your preferred industry). You'll probably take classes outside of your preferred industry because you were either curious about the field, couldn't make up your mind on which industry you want to go into, or were forced to take it as part of some requirement/certificate/"it was an easy class."
With that said, let's say you're this hot shot IB person who graduated from a top school, got into a bank, and then got laid off. Why would you worry or stress out about it at all? First off, you'll probably get a good severance package (up to 6 months I've heard), so you get a good vacation out of it. Second, you probably have some sort of secondary field that you always wanted to try out (maybe real estate? entertainment? entrepreneurship?) that now you have time to do. Third, you can call up your buddies in the different fields and see if you can get some referrals with their companies. And finally, you're resourceful, right? You could leverage all the skills and network you built during b-school to create your own career from that point on, ride out the bad times, and then get back into banking again when the times are good after a couple years (if you still want to go back into IB).
Times get tough for everyone at some point in their careers. I view it as an opportunity to try out something else, take the road less traveled, and maybe learn something from it. I graduated in 2001, when no tech company was hiring anyone. Interviewed with 15-20 companies and were just told during the interview that they're just at the career center for because of "formalities" and keeping their ties with the school. I ended up in an industry I wasn't too interested in, but made the best out of it. I do not regret my experiences over the past 6 years at all, and am glad to see an industry that I would normally never consider getting into.
Maybe I'm an optimist, maybe I'm simplifying things too much, but I feel that the piece of paper you get from this whole b-school process means much more than just a degree. A friend of mine said it best. "B-school doesn't really *teach* you anything you can't learn yourself. B-school is an experience that changes the way you think and approach problems/obstacles." I couldn't agree more.
My "2 cents"