Labels - useful or problematic?

There is debate as to whether labels are/can be useful or problematic.  Personally, I've found labels to be useful in many ways; from explaining to others what's going on for me, to receving the right treatment (some of which is only available if you have a specific diagnosis).  One label in particular was useful in helping me understand what was happening to me and why I felt a certain way. 

At the same time, I've not worn these labels with pride at any point.  They were useful on a personal level to inform me and guide me, but never to express who I was.  I never revealed them outside the therapeutic setting unless I had to.  On occassion, it helped me connect with others of the same diagnosis, but in general I lived in fear of being exposed/'outed'.  Mainly due to the unsavoury aspects of character alluded to in an array of related Google search results; stigma.  This was not something I wanted to put my name to.  Not something I wanted friends and family finding and assuming was true for me just because it was an opinion that someone, somewhere had of someone, somewhere they knew with the same diagnosis. 

Mental illnesses are not quite the same as their physical counter parts.  They cannot be seen directly and be scanned (for the most part) to detect something such as a 'break,' or a rash found and identified by referring to a photo.  Emotional pain is extremely difficult to verbalise and even harder to locate.  A label is not required for something such as a broken leg, as it is obvious.  People notice it, people sympathise, people try to help; they hold doors open and offer to carry things.  Mental illness is invisible.  People do not see it, people do not sympathise, and often do not try to understand.  Often people do not know what to do, and run away from it when we need their help the most.  We need to educate people, and tackle the taboo.  Are labels the way to go about this?  Are they ever useful?  What do you think?