Wikipedia has pages and pages of info about passive voice, including lots of examples of when passive voice is an appropriate construction. The Elements of Style by Strunk & White illustrates passive voice in several concise paragraphs, while making it clear that passive voice must be avoided at every opportunity. And then there's Steven King, who wonderful little book On Writing contains some of the best writerly guidance I've ever read--he hates passive voice. He seeks to destroy it at every turn, and recommends that I do so as well.
And yet, I've read an article that claims three of the four passive voice examples used by Strunk&White are not passive constructions, and that the authors actually mangle the guidelines for sentence construction quite thoroughly. And I've certainly dealt with a fair number of critique partners who seem determined to eradicate every form of the verb "be," even though its presence alone does not indicate a passive construction:
So. Lots of people are worried about passive voice. Most are convinced it's not the way to go. Some are comfortable spotting it; others are clearly confused about how to identify it at all. And I'm left staring at my MS, wondering if I should chop up my sentences and force them into forms that I'm not entirely sure are warranted. I mean, an obvious passive is easy to shoot down:
A lot of people think all sentences that contain a form of the verb “to be” are in passive voice, but that isn't true. For example, the sentence "I am holding a pen" is in active voice, but it uses the verb “am,” which is a form of “to be.” The passive form of that sentence is "The pen is being held by me."
The tent was filled with people
People filled the tent
As Steven King said (paraphrasing here):
The body should not be carried into the kitchen. It's a body for goodness sakes! It's not doing anything! Tell me John and Suzie carried the body into the kitchen, and I'm interested.