The real value of an MBA is the network you create with other MBA students.
That's why a Harvard MBA is worth more than (unknown school) MBA - the top companies hire Harvard MBAs who then have a business network with other Harvard MBAs - who of course got hired at other top companies.
I'd say it can be important. I'll also say that, having gone to a top-ish business school, other than getting a (fairly ordinary) job out of campus interviews, I never otherwise benefited from network/connections and mostly didn't stay in particularly close contact with most of my classmates.
Oh, connections can be important. 3 out of the 4 jobs I've had since grad school have been through people I knew and the 4th was an on-campus interview. But none of the subsequent jobs were B-school related in any way though one was peripherally related to undergrad.
I was mostly reacting to the meme that the only reason to go to B-school is the network and in my experience that's not really true and I'd discourage someone from attending for that reason alone.
That's why a Harvard MBA is worth more than (unknown school) MBA - the top companies hire Harvard MBAs who then have a business network with other Harvard MBAs - who of course got hired at other top companies.
It's self reinforcing.