The argument goes that the passive voice is weak because the subject – the person doing the action – is never stated.  For example: 

The lawn was mowed.

And we’re glad it was.  Me?  I don’t care who did it as long as it wasn’t me, but, as I am led to believe, that makes a sentence weak.  And therefore, it should never be used.  OK.  I’ll buy the weak part, but never?  Never?!  Comon!  Life’s too short for never.  I don’t want anybody limiting my writing.  That’s like saying, “Mr. Michelangelo, paint my ceiling, but you can’t use blue.”  And besides, how would politicians talk without the passive voice?  Because, as we all know, mistakes are made.