Once more, the New York Times has a solid piece on the definitions of generations, or the lack thereof.
The context is the presidential race -- is Barack Obama a Boomer or not? But the most important point of the piece for marketers is this:
"Generationality is not just what sociologists or advertisers decide. It is more crucially how one imagines oneself"True self-identity is indeed in the eyes of the beholder.
We use the Baby Boomer label only as a tool to identify a consumer group that deserves attention, and requires some new understanding from marketers in order to reach them successfully. Even if some argue the dates are hard and fast, what's more important is which generational cohort feels like the best fit for someone personally.