It's not always wrong, mind. It's particularly useful in technical reports when the subject is actually unimportant to the narrative and there's a desire for brevity, e.g.: The software was installed on the server.
And it can occasionally be useful in fiction to convey a feeling of helplessness or inability, e.g.: His measurements were taken, material and color decided upon, and the order was placed.
But too much passive voice tends to grate at readers, even if they're not sure why they're getting annoyed. In particular, I get jumped out of the narrative when I run into passive voice, largely because of something Lynn told me a while back.
She said that she learned to recognize passive voice by tacking "...by zombies" onto the end of a clause -- if it forms a useable sentence, then it's passive.
For instance: "The comic book was read... by zombies" does.
That lesson lodged in my brain as amusing and useful, and now whenever I spot a passive statement, I automatically tack "...by zombies" onto the end of it. Which, given my usual editing material, leads to some pretty hysterical results.
Blankets were tugged around them... by zombies.
The hair was brushed from the back of his neck... by zombies.
His shirt was pushed over his head, his jeans and briefs tugged down... by zombies.
Warm kisses were pressed to his ass... by zombies.
His cock was squeezed in a firm, hot grip... by zombies.
I'm just saying, here, that if I'm your editor and you get a note from me in the margin pointing out that something is in the passive voice, I've mentally rewritten your scene to include some zombies.
So you might want to do something about that.