I am currently working on some research that looks at the student loan system (both in the U.S. and abroad), and especially how it fits into the more general trends that set the sticker price for colleges and how students pay for them (loans, grants, scholarships, parents, jobs, etc.) I'll keep my discussion here based on graduate level loans and experiences.
One of the main points I'm having to make, especially in such a charged topic as this, is to be careful in separating the spectra of "responsible vs. irresponsible" and "right vs. wrong --or-- good vs. bad."
Part of the problem is that student loans, for a very long time, lets say, at least until 1988, but probably 1998, were unquestionably a good idea. The benefits of a graduate education, and experience, were great, and the loan terms (repayment, interest, government assistance) were amazing. There was at least one cadre of graduate students in poli-sci and economics the 1970s and 1980s that took out student loans, invested them, and turned a tidy profit before they had to be repaid (back when you could just return the entire balance after graduate and not incur fees or interest). A difficult proposition at this point, to say the least.
But, in the 1990s, repayment of loans changed. Legal changes made holding student loan debt a massive liability. It is nearly impossible to discharge student loan debt in a bankruptcy. And, unlike credit cards or any other loan which has a statute of limitations of 7 or less years (if you do not make a single payment on your credit card for 7 years, the debt goes away), student loans can follow you forever, and if you are REALLY irresponsible they can follow your parents or your children based on how long you live. In most states, two crimes have no statute of limitations--1st degree murder and not paying back your student loans.
So, student loans on their face are a tough loan to take. Put in the issues of graduate school, and the decision gets even harder. What if you don't finish? What if you take more than the advertised amount of time? What if some sort of emergency or life change requires you to take a year of leave--and the loan repayment kicks in? And these are just what might happen before you graduate.
At its heart, a student loan is a bet on what type of job you'll secure, and more importanly, how quickly you'll secure it. In some graduate disciplines, this is a easier choice than others.
So, my answer is that "is it fiscally irresponsible?" Absolutely. It is a loan on bad terms where you'll never have the legal upper hand, to secure an education that too often will take too long to pay off, if it ever does. This is particularly true for my colleagues who get paid stipends in graduate programs that could easily pay for living expenses in their cities, but take out more loans anyway because they want an extra bedroom or don't want a roommate, or have...habits...they need to feed.
However, "is it the wrong choice?" Probably not. "You got to pay the cost to be the boss." Besides, policies change all the time, and maybe things will get easier. It would be nearly impossible for them to get harder on those holding student loans.
I've gone swimming in the ocean during a hurricane. Irresponsible? Totally. Worth it? Without a doubt.