As creative types we are often influenced by the work of our peers and the work of our creative predecessors so it wasn't surprising that after a bit of research (ahem..googling) I discovered the source of the creative influence behind the Mad Men opening title sequence was the influential graphic designer Saul Bass.
From M.A. Peel at http://newcritics.com/But even if you aren't familiar with Saul Bass you are probably already familiar with his work. His portfolio consists not only of famous logo designs and posters, but also an impressive body of opening film title sequences, including Psycho. Among his later work was the title sequence for The Age of Innocence (which I watched again recently). At the time I remember admiring how beautifully the opening was done. I especially loved the subtle touch of the overlay of Victorian lace. Ah, but now I'm just rambling ...
I agree with with M.A. Peel. The Bass influence on the Mad Men opening title sequence is unmistakable.
Anatomy of a Murder - Opening title sequence
Here's a great quote from the man himself talking about his work.
"My initial thoughts about what a title can do was to set mood and the prime underlying core of the film's story, to express the story in some metaphorical way. I saw the title as a way of conditioning the audience, so that when the film actually began, viewers would already have an emotional resonance with it."- Saul Bass
Conditioning the audience? Yep, that's one I'll have to remember.