Since 2003, the Language Loggers have been looking at what people say about passives: what people identify as “passive” or “passive voice” (or, sometimes, alas, “passive tense”) and what as not; what they advise about the use of this syntax; and so on.
From the very first posting on passives, the Loggers have noted the inclination of a great many people to identify as passive voice any clause that is “vague on agency” (by failing to assign responsibility for some situation to a specific human agent). (Sometimes it’s clauses denoting situations that are not activities that are so identified.) The agency tradition continues, in two postings today, from Geoff Pullum and Mark Liberman, on Charles Krauthammer, here and here.
Concerns about agency and activity have led a surprising number of people (including many who really should know better) to identify as passive all clauses with the head verb be and to condemn such clauses as “weak”, “inactive”, “vague”, “boring”, and the like. But this fails in both directions: there are passive expressions that lack be and expressions with be that aren’t passive.