On the evening of Dec. 19, a Pantene commercial ran on U.S. television that skirted all the formal avenues of parent company Procter & Gamble's typical advertising process. Storyboards weren't pored over in P&G's Cincinnati headquarters. Average Americans didn't provide feedback in consumer research groups. Media planners didn't work for months in advance to buy advertising slots.

Instead, on Nov. 7, the one-minute commercial was released online in the Philippines by the local Pantene unit. It was never intended to reach U.S. viewers. And it was hardly an advertisement about shampoo at all.

Yet after four weeks online, it caught the attention of millions of Americans. So, plans changed. Fast. The video, which shows a male and female executive going through the same workday but experiencing different stereotypes based on their genders, is the latest in a line of viral ad campaigns that tap explicitly into a very raw, emotional sense of both female insecurity and empowerment. Dove did something similar earlier this year when it released an online video called "Real Beauty Sketches" about women's damaged self-image. That video has so far had more than 60 million views on YouTube alone.