ContactNorth provides a brief examination of the benefits and challenges of providing learning through online resources blended with a face-to-face component. The advantages of blended learning include the ability to create flexibility for students, the opportunity for faculty to experiment and engage with online learning at their own pace, and the ability to provide a higher level of student engagement. However, they warn that without the use instructional design principles, online learning components can be passive and content rich rather than engaging and challenging.
http://contactnorth.ca/trends-directions/how-make-most-blended-learning