Expanding on my previous post.
Say you have a BSEE and have been working as an engineer for Boeing for 10 years and you want to move into management; an MBA would be your best option, because your undergrad was in engineering and you probably didn't have any business courses. The MBA being a general degree will cover all of the functional areas of business (e.g., marketing, accounting, etc.)
Contrasting the above, say you have an undergraduate in business administration and you know! that all you want to do is human resources (HR). You would be better off getting a Masters in HR than an MBA because you already had a foundation in the functional business areas in your undergrad program.
Many companies expect their employees to want to progress up the career ladder, and a graduate degree combined with experience is a great option. Just know what you want to do and where you want to go. As a side note, a graduate degree in math, statistics, operations research, or another quantitative area would give you plenty of options for employment as a statistical analyst, statistician, or so forth. At work I was joking with a statistical analyst/SAS programmer that I wanted his job (I am a Unix admin). He said they could always use more analysts because they cannot find enough of them (which I believe to be a very true statement). But you usually have to have a graduate degree (which is usually heavy in research and stats) for that type of position, but the pay is usually much higher than the average pay.