In my humble opinion it does not really matter that much how good is the economy at the moment of graduation (in the short run).
We will all end up working for many many years in the future, prolly even up to 30-35 years or more and its definetely better option to be paid as an MBA versus BA or stuck up with a job that u dont like.
Even though if u graduate in the peak of a recession u will catch something, maybe not very well paying but what the heck, just to survive for a year or to till the market goes up again and raises bonuses and salaries.
The thing is that in times of bad economy a lot of ppl who really dont have anything else to do will end up applying to the bschools and thus take some spots from ppl who really wanted it.
That kinda sucks.