I noticed on one of the message boards a person asking if the rumors he's heard of a certain manga (not mine, thankfully) being badly translated are true.
Most rumors of a bad translation are false.
First, let me define a bad translation. It's what you first think of when you hear the words "bad translation." That there are major mistakes in the information that is put across. That the information contained within the English words are significantly different than the information contained in the Japanese words. This is not about stilted dialog and not about characterization that doesn't meet your expectations. This is about mistakes. The reason why I say that is when most people hear the words "bad translation" they take from it the idea that the information is wrong -- not simply that one critic disliked the style.
The main problem with taking the "bad translation" judgement at face value is that not even some professional translators can distinguish between an actual mistake and a difference of interpretation. It takes one going through the "Greatest Translator in the World" stage (see the previous entry -- Journeyman/Black Belt 2nd degree) to really give other translators the benefit of the doubt. Before that, even professional translators are so insecure about their own interpretations that they see other interpretations as a attack on their view. That generates an emotional response that causes even some professionals (and nearly all amateurs) to proclaim that any interpretation other than their own is wrong.
Let me see if I can explain the difference between a different interpretation and a mistake. There are two ways to look at differences between your translation and someone else's translation. One would be seeing the other translator making a mistake that you can understand as a mistake. For example mistaking "sore wo shi na" (do that) with "sore wo suru na" (don't do that). That's a mistake -- and a translator can understand how the mistake was made (the original translator mistook one use of "na" for another).
But if someone took the phrase "shikata ga nai," which normally translates out as "there's nothing that can be done," and translated it to "I'm screwed," then it may not be the way I'd translate it, but it has the meaning of not being able to do anything about the situation and is therefore not a mistake. It's a difference in interpretation. It's a "legal" translation, and by whatever unwritten rules of translation I've been able to figure out, it's can't count as a "bad translation." Any translator who has yet to go through the humbling process that ends the "Greatest Translator in the World" phase will probably consider the "I'm screwed" translation as a mistake -- and write a column on the net saying the book is a bad translation. Fans hear it and spread the rumor. And since translation is all about reputation, the translator, who's only fault is to be read by the wrong person, might not get his or her next job.
So until a person has been translating professionally for three or four years, that person is really not qualified to judge whether something is a good translation or not. (And really, by that time translators are so busy with their own work that they don't go around judging other people's translations.) What that means is that very few of the "bad translation" rumors are being spread by people who are qualified to judge.
A mistake is a mistake, and those should never happen in a translation. But they do. The more experience a translator gets, the less mistakes you'll find -- but there still are mistakes. I've been translating for more than 15 years, and some of my translations still contain mistakes (please don't go looking for them). They'll be tiny mistakes and won't affect the way the story plays out, but humans are mistake making machines, and the last time I checked, I'm still very human.
If a translation has enough mistakes to change the tone of the story or change the way a character seems to the reader, then it may be considered a "bad translation," and I'm sure there are bad translations out there, but who is making that judgement? And just how qualified are they to make it?