In dating, the friend test -- how well you mesh with your new flame's friends -- is critical to the future of your relationship. For marketers targeting Generation Y, the friend test may be just as significant.

Taco Bell is speaking Millennials' language with its latest campaign for its steak burritos; the ad tells guys it's perfectly acceptable to still want Taco Bell (no doubt a staple of their teen years) even if they can afford dinner at a steakhouse. It doesn't make them any less grown-up to still like the things they did when they were thirteen.

We have been living with multiple personalities for years. Millennials have been known to show varying sides online, way before the chatter began around the benefit of the "Circles" capability in Google+.