Is it wrong to write in passive voice?
It may be considered "weak" but never wrong as long as it's constructed correctly. However, as many of these answers imply, there are "good/better/best" contexts for the use of passive voice. Here are two specific contexts that will be helpful to many students: SAT questions & news writing.
The official SAT practice book refers to the "weak passive verbs." These are found in Sentence Improvement questions. Most of the time, a straight forward active voice answer choice is a better answer than a weak passive voice answer choice. (However, in the last decade, I have seen some real tests questions with a passive voice answer as the best answer, so don't automatically assume it's wrong.) Generally, it's also best to use active voice within SAT essays.
Traditionally, news writing requires the use of Subject-Verb-Object sentence structure. This is inherently active voice. Passive voice in news writing is usually either found in a direct quotation or in reporting information that is not complete.
Lastly, be sure that you fully understand the construction of passive voice construction. (It's not just the feel of the sentence.) The object is moved to the subject position and the verb becomes a participle with a to be helping verb. Here are two examples of passive voice based on rearranging this active voice sentence: Bob ate all the cookies. (S-V-O)
(1) All the cookies were eaten. (O-V The object is now the subject, and we don't know who did it.)
(2) All the cookies were eaten by Bob. (O-V-S The actor is now an object and less central.)