Hey gang, here's my conundrum:
In a game, I recently discovered an enchanted item: a magical flute. I proceed to cast Identify on it and this happens:
"Yes it is magical."
"How do I use it?"
"By playing it."
"What does it do?"
"You'll have to play it to find out."
So I do. And I "play a lovely melody, only to discover that you cannot speak."
The spell reads this way: "You learn its properties and how to use them, whether it requires attunement to use, and how many charges it has, if any, whether any spells are affecting it and what they are."
I took Identify because I HATE booby-trapped items. Should I not have gotten the heads up on this thing? And I still have no idea what the melody DOES, shouldn't I know that too? I thought the point of Identify was to keep this kind of thing from happening.
Thanks for the input. Happy gaming, all! 
That is the point of identify. If your group is an experienced group of players, the vague description on the item would have been an enormous red flag. If you're new to the genre, then that was kind of a jerk move on the part of the DM. It's a cursed item. Read: the DM wants to screw with you.
Your DM is either A) unfamiliar with how the identify spell functions, or B) intentionally bypassing the written rules with malicious intent.
Have a conversation, politely and outside of session time, to show the DM the identify spell and explain what you expected it to do when you cast it, and if the result is anything except for an apologee for a bad call in the described situation, immediately cease playing with that DM and tell him why you are ceasing - the only way to show a DM that their bad calls aren't going to be tolerated is to actually refuse to tolerate them with no exceptions.
You can trust me that "I'll just keep playing and keep expressing that I don't like it when he does something I don't like," is only ever going to result in the bad-call DM thinking you are enjoying his calls just fine, unless the DM acknowledges the bad call the first time you point it out and makes changes.
It's probably that your DM is an "old-school" DM, or was taught by one. In the olden days, cursed items specifically weren't pointed out by the Identify spell. They were an ultimate "gotcha" mechanic for the DM, because there was literally no way to know an item was cursed until you used it. You're just suddenly stuck with the bill for a Remove Curse spell, and hoping that the one who has that spell isn't the one who just lost his voice (can't cast spells without vocal components).
This is a different era, though, and pulling that kind of BS is less tolerated, and for good reason. I advise that you make it very clear to your DM that you don't appreciate the arbitrary boning of your character.
As an "old-school" DM, I have to say that Novacat is giving too much credit - even back then you would get to know something about the item if its curse wouldn't apply until you used it.
Rather than "you'll have to play it to find out," as the example was in the original post, it would have been something like "playing the flute seems to summon a swarm of rats that acts as the user commands," and then when you play it to get that beneficial outcome something bad happens instead.
Much like how a cursed weapon would appear to be some kind of beneficial magical weapon so that it could actually trick someone into using it so that it could curse them.
Pretty much never has identify provided results of not at all getting to know anything about an item without first using the item.
Yeah, sounds like some Wheaton's Law violations to me.
Dash_Headlong wrote:
As an old school, bastard of a DM myself, if I had included an item like this in my game (and I might, for player's who've been around a while and should know better) here's how I would have handled the Identify spell. Note that this "ruling" is before the Dungeon Masters Guide comes out with any possible rules about cursed items.
"The item is a flute of vermin. By playing different melodies you can summon and charm up to 3d6 hit dice worth of various small creatures such as rats and mice, ground squirrels, rabbits or other agricultural pests. This feature works once per day. On a Charisma check of DC18 or higher, you can summon and charm humanoid children once per week. None of these features work on undead, constructs, or creatures immune to charm. The item is not charged, and there are no individual spells cast upon it. You determine that there is some sort of cost for using this item, known as "paying the piper," but not what that cost is. The item can be used by anyone with proficiency in a musical instrument and does not have to be attuned to use."
Depending on how experienced my players are, I might give them a History or other check to identify what "paying the piper" means, or the research might become a side quest in the campaign. But (remember, I'm an old school bastard of a DM) I would feel justified that warning them about "paying the piper" was enough to let them know that there was more to this item than meets the eye and to be cautious. If they still went ahead and just played the flute to see what happened, I'd be satisfied that they got what they deserved.
If the players were newbies, I'd tell them the properties of the flute including the "cost," and let them decide whether it was worth it.
Thanks gang. Had a good talk with my DM and got everything straightened out.
Happy gaming! 
Noctaem wrote: