I've dealt with that same situation quite a bit.  Requirements gathering is the task it seems no one really wants to do, and unless it's strictly enforced, it's a nightmare.  On the same note, I've had more then a few times where I've ended up completely refactoring a project because the end user didn't know what they wanted.  A couple times because they outright refused suggestions I made as not what they needed.  That is until they saw what they thought they needed, and complained it wasn't what they really needed :/