Will Wilkinson has a smart column on one of the many problems that besets happiness research: pollution from moral ideas about what ought to lead to happiness.
Most of us have all been raised with ideas about "the good life," and we are prone to see happiness in such a life -- honest, hard-working, devoted to family and friends, in touch with nature, etc. Presented with a person who seems to be happy but is partying all the time, using lots of drugs, lying, treating friends badly, using other people sexually, and whatnot, we are quick to say that this person cannot really be happy. (Wilkinson's essay takes off from a study that shows exactly this.) We judge our own lives using criteria we learn, mostly, from these sorts of social expectations.
Our knowledge of who is happy comes from what people say about themselves, and what they see in the lives of others. Neither kind of data is even close to objective. What, in this context, would objectivity even mean?