In his Writing Tools blog, Roy Peter Clark has an interesting take on active vs. passive.  As you know, passive voice has long been criticized as being, well, too passive.  Active voice, on the other hand, is generally seen as being more powerful and persuasive.  Clark, however, points out that the two voices can be used together very effecively.  Read his example here.  This is the writing tool to remember: 

When you are trying to emphasize the victim or receiver of the action, use the passive voice. But when the subject turns to direct action, use the active voice to describe it.