Should graduate study be done when you are not fully interested in the subject matter? This question is somewhat broad, but this place seems like the best place to ask. I have been accepted for an information assurance program, but I am a computer science major and my main interest lies in software development. Should that deter me from deciding to study information assurance?

Another factor in the decision is that the program is through scholarships for service, so it is a 2 year program with 2 years of work in a government position for information assurance. Ultimately, I recognize it is a subjective decision. The core question I am trying to ask is, should you do graduate study even if you are only partially interested in the subject matter? In other words: how committed do you need to be to the subject matter for graduate study to be worthwhile?

On another note, we continually see news about huge networks with cybersecurity issues. Sony's Playstation network, LinkedIn, and I think I read today that Yahoo! accounts may have been compromised. With the growth of businesses and services online, it seems only natural that an adept skill-set in information assurance would be beneficial.
An unmotivated graduate student will usually be a lackluster student at best. These students will be more likely to be distracted by whatever their true interests are. 

Moreover, in a program like the one you are describing, you will be making a very significant career detour. You would be advised not to make such a move unless you are absolutely sure that it's something you'll want to do for the next four years, since you will have a payback requirement. If you're not sure about it, this is the kind of move that can wreak havoc on your career—particularly if you (re-)discover your dissatisfaction after the classwork is complete, and the service period begins.