How important are grades?
For me, the grades I received had a direct impact on my finances, as my employer reimbursed 100% of tuition and books for an A, 90% for a B, and 70% for a C. I had to pay a few hundred out of my pocket because I received two grades of B+.
Getting a 3.9 GPA placed me in the top 20% of my graduating class, which earned me an invitation to the Beta Gamma Sigma Honors Society. So what good is that? I get to mention my membership in my resume, for whatever that is worth. The Beta Gamma Sigma San Francisco Area Alumni Chapter offers a LinkedIn Group which enables fellow members to search each others profiles and contact each other directly via LinkedIn. The chapter also offers interesting events such as a career panel. So far, I've had no use for any of the benefits of being a member of the society, but perhaps the benefits will be useful at some point.
Do recruiters care about grades? According to a recent article in BusinessWeek and comments on Harvard Business Reviews' Working Knowledge site, it appears that recruiters do use grades as one factor for evaluating recruits.
Do grades alone provide a foolproof indicator of success in business (however you may define that, e.g. contribution to the bottom line)? Of course not. You may find in the long run that your time was better spent getting to know your classmates better as opposed to doing extra work to earn an A- rather than a B+. The classmates you meet may be connections which enable future success. On the other hand, if you're aiming for a B rather than an A in a class which involves groups projects, your lack of drive for an A may irritate your teammates and cut off potential future opportunities. I personally wanted my classmates to remember me as a person with high standards, who would do whatever it took to get the best grade possible without making any ethical compromises.
Some argue that grades provide the wrong incentive for students, and that students should focus on learning as opposed to acheiving high grades. While I can agree that there could potentially be a conflict, I never felt that I had to make any significant compromises in my quest for learning to obtain high grades. I use the qualifier "significant" because there were a few times when I would tweak my study habits, homework, and test answers to give professors what I thought they wanted. But is that so bad? If you look at a professor as a "customer" who wants a certain "product", then a good business person would deliver what the "customer" wants to get the highest "returns" (grades).