It’s no doubt that social gaming is wildly addictive. On Facebook alone, games like Scrabulous, MouseHunt, and Texas Hold’Em have become overnight success stories, gaining popularity and large audiences. Now, businesses are starting to see that they, too, can tap into the combined power of the social graph and game design to win not points, but customers.

The latest story is that of Kaplan, the renowned test prep company that recently released QBank, a Facebook app designed to quiz, rank, and reward medical students in their second year embarking on the journey that is USMLE (US Medical Licensing Exam) preparation.

Since its inception this February, QBank has already gained a loyal following of more than 2,500 Facebookers. This is impressive for such a niche audience since the QBank questions are geared only for second year medical students.

QBank’s approach is fairly straightforward and anyone can add the app and play. Gaining points is another story — getting to the top of the leaderboard will likely take some serious medical knowledge. If you think you’ve got what it takes to pass the Step 1 of the USMLE, then you can try your hand at the sample questions offered through the QBank app. There are three new timed questions per day and points are awarded for speed and accuracy. The site also offers test takers a common meeting ground and a platform for discussion.

Kaplan’s strategy is smart — they understand how busy medical students are and they are willing to reach out and offer services to their customers on a platform that’s already familiar and widely used. If Kaplan’s test prep is as good as its marketing, there’s no need to worry about results — it’s clear that both the company and its clientele will fare well.