Necessary to life? No. Necessary to life satisfaction? No, not an entire formed identity or fully stable one.
It's not really necessary, I think. But if you really want to be happy and comfortable fully in yourself and the social systems, then, yes, it's needed. Even if it's only half of one. Because having an identity is what sets you apart from all the other humans (or cakes, according to [MENTION=6917]sprinkles[/MENTION] - Good analogy btw). Without a social system or society...we wouldn't need much of one, would we? However, it does exist in us. We have traits from the Nature side of the Nature vs. Nurture argument. And Nurture isn't so much how we were raised but collective experiences from interaction with...well, life. We have our own ways of functioning and our own realities. No denying that. But most of the pressure to form an identity is from the pressure of the society on the individual. We all have one already. Just we aren't all aware of it, due to life inexperience, not enough knowledge on certain subjects, etc.
Personally, I want to know myself more. Look at myself from the outside and just come to know "me". Little hard to do that because, you know, I'm the subject. Haha. But I hate the idea of waiting and you'll discover yourself that way. That's a good way to do it but so inefficient. But I'm comfortable with waiting. I have a very balanced faith (logically consistent in itself and the world outside of it and emotionally fulfilling) and by really looking into the belief systems and arriving at the same conclusions...it helps a lot. "I believe this, this, this and that and here's why." on lots of matters. Not to mention, you know, the whole personality system that unites us on here? Yeah, that helps, too. Even things I haven't experienced yet and I don't understand what is meant. After some more thinking or social interaction, I realize I feel/think/act quite similar. Example: "Basically, love for an INTJ, means they include you in their vision of the world." I was going over my 3 decade some life plan thusfar with another INFJ. And when discussing marriage/dating briefly, it clicked and I thought back to that idea on a couple INTJ relationships/profile pages I've read. "I understand now. I have this vision of my life. And, things I've come to love in this world, I include in it." No one person yet but one day...maybe. And they'd be a special person, indeed.
No matter what, though, I'm still me. Individual and unique thoughts, feelings, and reality. And there will be no other existence exactly like my own. And I'm determined, that since I'm here, existing and all that, mine-as-well make the most of it and be content.