Pink gets huge by targeting the core

Brandweek has a great, fairly in-depth piece on Victoria's Secret's Pink sub-brand:

Today, with sales of $1 billion, Pink has indeed become that megabrand that headquarters dreamed about just a few years ago. Pink is, in fact, one of the bright spots in a year in which Victoria's Secret has suffered a drop in business. Cohen predicts that Pink will continue to be a pillar for the company but, in fairness, that's partly because Pink has no real competitors (for now) within a category it largely pioneered on its own. "No one is nipping at their heels," Cohen said. "You could look at Abercrombie [& Fitch] and American Eagle, but not quite. Pink is an attitude. American Eagle and Abercrombie are lifestyles."
...
Success would mean slicing the population as thin as a lingerie strap—women aged 18 to 22—but the brand message, if delivered correctly, was just what that group wanted to hear. "It's a very smart strategy," Cohen said, "because every 16-year-old wants to be a 19-year-old and every 24-year-old wants to still live like a 19-year-old."

My take
If I had to boil lifestyle marketing down to one simple idea, it would be this: a successful lifestyle brand must always, always stay true to the core. Keep the core happy and they'll do much of your marketing for you. Sell them out, and they'll turn from passionate evangelists into vocal opponents of your brand. Pink is proof that, if you choose the right segment as your core, the sky is the limit- in this case, to the tune of $1 billion in annual sales.